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16 Airports and Clean Vehicle Programs General Airport Overview The airports surveyed for the current study represent seven of the nine FAA regions of the United States. The Alaskan and Southwest regions were not included. Table 2 presents the list of FAA regions and the states included in each region. The largest number of surveyed airports were located in the Western-Pacific region, followed by the Northwest Mountain region of the country. Due to a relatively low number of surveyed airports, most of the regions are represented by a single airport. Figure 3 summarizes the number of airports surveyed from each FAA region. FAA categorizes commercial service airports into broad categories based on the types of activities and the amount of passenger traffic handled by the airports. Commercial service airports that handle 1% or more of the annual passenger boardings in the United States are commonly referred to as large hub airports. Airports that handle from 0.25% to 0.99% of national annual passenger boardings are considered medium hubs. Airports that board at least 0.05% but less than 0.25% of all passengers in the United States annually are small hub airports (FAA, 2017b). Eight of the 11 (73%) surveyed airports are large hub airports with average enplanements of 20.5 million passengers per year. Two airports are medium hub airports enplaning on average 5.1 million passengers per year, and one airport is a small hub with 1.3 million enplaned passengers annually. An average airport from the group of surveyed airports enplanes 15.9 million passengers per year. Figure 4 summarizes the hub status of the airports surveyed. Six (over half) of the 11 surveyed airports are located in nonattainment areas for one or more criteria pollutants as defined by NAAQS. Additionally, one surveyed airport is located in a main- tenance areaâan area recently in nonattainment status that is currently meeting air quality stan- dards. Only four surveyed airports maintain attainment status. Nonattainment status is one of the motivating factors for airports to implement clean vehicle programs and other sustainability practices. However, with recent improvements in conventional vehicle technologies, the advantage AFVs offer in the amount of criteria pollutants emitted has decreased dramatically, sometimes to the point of being negligible. Therefore, many AFV projects currently focus on GHG emission reduction rather than the air quality improvements provided by AFs. Figure 5 summarizes the attainment status of the surveyed airports. All the areas in the current study that are in nonattainment or maintenance status are in viola- tion of air quality standards for ozone, and more than half of the areas (four surveyed airports) violate emission standards for fine particulate matter (PM2.5). Fine particles in the air (with a C H A P T E R 3 Results
Results 17 diameter of 2.5 µm or smaller) are particularly dangerous to human health because they stay longer in the air than larger/heavier particles (e.g., PM10) and when inhaled are able to get deeper into the lungs, causing serious health problems. Figure 6 summarizes the types of criteria pollut- ants that affect surveyed airports located in nonattainment and maintenance areas. Alternative Fuels and Sustainability Practices Although airports are not necessarily the primary cause of poor air quality in nonattainment areas, they contribute to an areaâs emissions. Airport sustainability programs aiming to reduce FAA Region Name Region Code States Included in the Region Alaskan AAL Alaska Central ACE Iowa, Kansas, Missouri, Nebraska Eastern AEA District of Columbia, Delaware, Maryland, New Jersey, New York, Pennsylvania, Virginia, West Virginia Great Lakes AGL Illinois, Indiana, Michigan, Minnesota, North Dakota, Ohio, South Dakota, Wisconsin New England ANE Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont Northwest Mountain ANM Colorado, Idaho, Montana, Oregon, Utah, Washington, Wyoming Southern ASO Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, Puerto Rico, South Carolina, Tennessee, Virgin Islands Southwest ASW Arkansas, Louisiana, New Mexico, Oklahoma, Texas Western-Pacific AWP Arizona, California, Hawaii, Nevada, Guam, American Samoa, Mariana Islands Table 2. FAA regions. 1 2 1 1 4 1 1 Eastern (AEA) Northwest Mountain (ANM) Great Lakes (AGL) New England (ANE) Western-Pacific (AWP) Central (ACE) Southern (ASO) 0 1 2 3 4 5 Figure 3. Number of surveyed airports by FAA region.
18 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Small 1 Medium 2 Large 8 Figure 4. Surveyed airports by hub status. Attainment 4 Nonattainment 6 Maintenance 1 Figure 5. Airportsâ attainment status. 7 1 1 4 Ozone NOx PM10 PM2.5 N um be r o f A irp or ts Figure 6. Criteria pollutants at nonattainment and maintenance surveyed airports.
Results 19 the airportâs environmental impact can have a noticeable impact on the areaâs GHG emissions and local air quality. All surveyed airports reported using and encouraging one or more sustainability practices intended to reduce emissions. The most popular strategy is the use of AFVs. Nine of the 11 (81.8%) surveyed airports reported using and/or encouraging AFVs. Additionally, three air- ports reported using/encouraging fuel-efficient and low-emission vehicles such as hybrids. Five surveyed airports reported employing restrictions for vehicle idling. Some airports have no explicit anti-idling policy but use strategies that lead to reduced vehicle idling, such as providing free parking and air-conditioned rest areas and/or employing strict antistaging rules. The first strategy enables drivers waiting to pick up passengers to park their vehicles and wait in a comfortable climate-controlled area instead of waiting in the car with an idling engine. The second strategy restricts waiting at the curb and prohibits engine idling unless the vehicle is being loaded or unloaded. Each of these strategies was used by two surveyed airports. It is worth noting that these two strategies are most effective when applied together. An antistaging rule alone may lead to increased circular traffic around the terminal, actually result- ing in higher vehicle emissions. Finally, three (27.3%) surveyed airports either employ or encourage private GT operators to implement strategies that reduce empty rides. An empty ride is any vehicle trip of for-hire vehicles made without passengers, including trips to pick up passengers and return trips after passenger drop-off. This is also referred as âdeadheading.â Figure 7 summarizes common sustainability practices at the surveyed airports. All the surveyed airports encourage the use of AFVs at the airport through formal or informal policies, and some airports even require GT operators to use AFVs. Major commercial airports often use various AFs in airport-owned fleets to meet the environmental goals of the airport. However, even airports that actively use AFs in their own fleets are not always willing to require private GT operators to use AFVs. Although almost all the surveyed airports encourage GT pro- viders to use AF and other clean vehicles, such encouragement is often informal and does not provide any incentive for operators to comply. The surveyed airports appear to favor natural gas and EVs over other types of AF technologies for airport-owned vehicles. Ten of the 11 surveyed airports use vehicles in their fleets that run on CNG. Five airports use propane-powered vehicles, whereas six surveyed airports reported having 9 3 5 2 2 1 3 0 2 4 6 8 10 Use of AFVs Use of fuel-efficient/low-emission vehicles Restriction of idling Antistaging rules Offer parking/rest areas (free or low cost) Encourage transit use Strategies to reduce empty rides Number of Airports Figure 7. Sustainability practices at surveyed airports.
20 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers battery EVs in their fleets. Additionally, four of the 11 surveyed airports use biodiesel-powered vehicles. Other types of AFVs include those run on renewable natural gas (RNG), renewable diesel (RD), liquefied natural gas (LNG), hydrogen, and plug-in hybrid-electric vehicles (PHEVs). Figure 8 shows the types of AF vehicles commonly used in airport fleets. The number of airports using different types of AFV technologies in Figure 8 adds up to more than the total number of surveyed airports (11 airports) because most of the surveyed airports reported using multiple AF technologies in their fleet vehicles. In addition to using AFVs in their own fleets, airports may encourage private GT providers to use AFs or other clean vehicle technologies. Some airports have clear preferences for technolo- gies because of their potential contribution to the airportâs sustainability goals. If that is the case, airports encourage GT fleets serving the airport to use those specific AFV technologies. Other airports endorse all types of alternative technologies and fuels that can produce environmental benefits to the local area. Still another approach involves encouraging private GT operators to use vehicles with certain fuel efficiencies or tailpipe emissions equivalent to those of AFVs. These options lend more flexibility to private operators. The responses from the surveyed airports indicate that the AF technologies they most often encourage private GT fleets to use include CNG, electric, and propane. Six surveyed airports encourage private fleets to use CNG vehicles, five airports encourage the use of EVs, and three airports encourage the use of propane-powered vehicles. The popularity of natural gas and electric vehicles is likely attributable to the tailpipe emission benefits associated with these technologies. Anecdotally, several airports indicated that they consider CNG and electric vehicles superior in terms of emissions benefits compared with the other AFV technologies available. Hybrid-electric vehicles, plug-in hybrids, and vehicles with emissions comparable to AFVs were each encouraged by two surveyed airports. One airport encouraged private fleets to use vehicles with a minimum fuel efficiency of 45 mpg. Other technologies and vehicles encour- aged by the surveyed airports include RNG, RD, LNG, and biodiesel. Figure 9 summarizes the clean vehicle technologies the surveyed airports encourage private GT fleets to use for airport operations. Airports usually encourage private GT providers to use multiple clean vehicle technologies, which results in different types of AFV technologies being used by a single airport; in Figure 9, the number of airports using different types of vehicles adds up to more than the total number of surveyed airports. 4 10 6 1 2 5 1 1 1 0 2 4 6 8 10 12 Biodiesel (BD) Compressed Natural Gas (CNG) Electric (EV) Hydrogen (H) Liquefied Natural Gas (LNG) Propane (LPG) Plug-in Hybrid (PHEV) Renewable Diesel (RD) Renewable Natural Gas (RNG) Number of Airports Figure 8. Types of AFVs used by airport fleets.
Results 21 All surveyed airports reported having AF stations on airport property or near the airport. CNG fueling infrastructure is by far the most popular type of alternative fueling infrastructure, followed by electric. All surveyed airports reported having a public-use CNG fueling station at or around the airport property, and six of the 11 (54.5%) surveyed airports have public EV charg- ing stations at the airport. Most surveyed airports have more than one type of alternative fueling at or around the airport, mainly in line with airport preferences regarding the types of AFVs in their own fleets. Figure 10 describes the types of alternative fueling infrastructure available at or around the surveyed airports. Fueling infrastructure located on airport property can be owned by the airport, a municipal- ity, or a private fuel supplier. Whatever the case, all surveyed airports recognize fleet access to fueling infrastructure as one of the most important success factors in promoting higher AFV usage at the airport. Clean Vehicle Policies Six of the 11 surveyed airports reported having a formal clean vehicle policy that applies to private GT providers, whereas five airports have no formal policy. Additionally, two airports reported having informal clean vehicle policies for private operators. The informal policies were 1 6 5 2 1 3 2 1 1 2 1 0 1 2 3 4 5 6 7 Biodiesel (BD) Compressed Natural Gas (CNG) Electric (EV) Hybrid-electric (HEV) Liquefied Natural Gas (LNG) Propane (LPG) Plug-in Hybrid (PHEV) Renewable Diesel (RD) Renewable Natural Gas (RNG) AFV Emission-comparable Vehicles Fuel-efficient Vehicles (45+ MPG) Number of Airports Figure 9. Vehicle technologies that airports encourage private operators to use. 1 11 6 1 1 Biodiesel CNG Electric Propane RNG N um be r o f A irp or ts Figure 10. Alternative fueling infrastructure at or around surveyed airports.
22 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers vague and involved a general suggestion of using sustainable practices by GT providers or a recommendation to work on reducing GHG emissions at the airport. Because of the informal nature of these policies, no evaluation of compliance was provided and no impact assessment was available. Figure 11 demonstrates the share of surveyed airports with clean vehicle policies that apply to private GT providers operating at the airport, and those without formal policies. Airports can manage airport-permitted GT operators through their contracts. Although airports may not be able to directly regulate GT, they can exercise contractual authority to manage ground access. Airports with formal clean vehicle policies typically employed one of the following five types of policies. Explicit Requirement for AFV Use The airport requires operators to use certain types of AFVs. Phoenix International Airport (PHX) uses an explicit AFV requirement. All contract operators (taxis and shared van rides) operating at PHX must run dedicated AFVs, including those using CNG, propane, electric, and other technologies. PHX does not mandate that other operators use AFVs but offers discounted trip fees for using dedicated AFV technologies. Fuel Emission Standards The airport requires transportation providers to operate AFVs or vehicles that meet a certain minimum tailpipe emission standard comparable to that of AFVs. Los Angeles International Airport (LAX) employs a policy with vehicle emission standards. LAX requires all vehicles with a gross vehicle weight rating (GVWR) of 8,500 lb or more to use AFVs or vehicles comparable to AFVs in terms of emissions. The policy does not define hybrid-electric or bi-fuel vehicles as compliant with clean vehicle policy for medium- and heavy-duty vehicles. Appendix D provides more details on the clean vehicle policy at LAX. Minimum Vehicle Fuel Economy Requirement The airport requires transportation providers to use vehicles for airport operations with a cer- tain minimum fuel efficiency. Seattle-Tacoma International Airport (SEA) has a clean vehicle pol- icy that includes a minimum vehicle fuel economy requirement. Taxicabs at Seattle International Airport must operate vehicles with a fuel economy of 45 mpg. This requirement is written in the airport concessions agreement with taxis. SEA also requires similar efficiencies from transportation network companies operating at the airport. If TNCs operate vehicles with lower fuel economy, they are subjected to higher airport fees. Incentive for Using AFVs The airport employs an incentive program providing lower airport fees to transportation providers that operate qualified AFVs at the airport. Operators can choose to operate any kind of vehicle but will face full fees if vehicles are not AFVs. San Diego International Airport (SAN) uses an incentive-based clean vehicle policy. All airport-permitted commercial GT operators, includ- ing taxicabs, vehicles for hire, hotel shuttles, off-airport parking shuttles, rental car shuttles, and transportation network companies, are allowed to pay lower airport fees if they operate alterna- tive fuel or clean air vehicles, including those using CNG, propane, RD, or electricity and plug-in hybrid vehicles. The requirement for TNCs is more performance based and provides incentives Formal policy 6 No formal policy 5 Figure 11. GT fleets with clean vehicle policies.
Results 23 not only for AFV use but also for ride sharing and other strategies for reducing VMT. Appendix D provides more details on the rules and regulations at SAN. Penalty for Not Using AFVs The airport imposes higher fees on GT fleets for operating non-AFVs. Operators can choose any kind of vehicles but will be penalized by higher (sometimes significantly higher) fees for not using AFVs. San Francisco International Airport (SFO) uses a penalty-based clean vehicle policy. Courtesy shuttle operators at SFO incur triple trip fees for all trips made in vehicles not operating on AFs (CNG, EV, PHEV). The airport mandates that shared van rides use only CNG vehicles, whereas other types of operators (taxis, limos, TNCs) are not subject to the AFV requirement. Appendix D offers more details on the clean vehicle policy at SFO. In addition to the mentioned types of policies, some surveyed airports impose requirements and recommendations for GT operators to reduce empty rides. This requirement mostly applies to TNCs. The most popular clean vehicle policy among the surveyed airports (three surveyed airports) requires the explicit use of AFVs by GT operators. The requirement to use various strategies to reduce empty rides is also used by three surveyed airports. Penalty-based policies that impose higher airport fees on operators that do not operate qualified AFVs were used by two surveyed airports. Other types of clean vehicle policies were less popular with the commercial airports. Figure 12 summarizes the types of clean vehicle policies airports use for private GT operators. Different types of clean vehicle policies may apply to different types of GT providers. Air- ports choose to manage providers based on their type of operation, vehicles used, whether the airport is a primary (significant) market to the operator, and other factors. For example, CNG is most appropriate for medium-duty and heavy-duty vehicles that have adequate space for fuel tanks and do not have significant weight limitations. Smaller light-duty vehicles have limited space and weight capacity for CNG fuel tanks of adequate size/range. Therefore, GT providers that operate larger vehicles, such as vans, shuttle buses, and large buses, are more likely to be subject to a CNG vehicle requirement than are operators that run mostly light-duty passenger cars. Applying different clean vehicle policies to different types of GT providers is common for several of the surveyed airports. For example, although shared van ride operators at SFO must use CNG, other airport GT providers, such as taxicabs, limos, and TNCs, are not subject to the AFV requirement. 3 1 1 1 2 3 0 1 2 3 4 5 6 Explicit requirement of AFV use Fuel emission standards Minimum vehicle fuel economy requirement Incentive for using AFVs Penalty for not using AFVs VMT (empty rides) reduction strategies Number of Airports Figure 12. Types of formal clean vehicle policies at surveyed airports.
24 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers In addition, anecdotal evidence suggests that few airports impose any restrictions on the type of vehicles operated by limousine or transportation network companies. Limousine companies operate luxury vehicles that are not always available in a âclean vehicleâ version. TNCs use pri- vate vehicles and do not have any control over the types of vehicles used by individual drivers, making it difficult to impose and/or enforce any clean vehicle standard. The following is a discussion of the types of clean vehicle policies and regulations that apply to different types of private GT fleets as reported by the surveyed airports. Taxicabs Taxicabs are traditional airport GT operators and are usually regulated by local jurisdictions (city or county commissions). Surveyed airports that administer additional requirements on taxicabs and impose formal clean vehicle policies typically employ one of three types of poli- cies: an explicit requirement to use AFVs in the taxicab fleet, a requirement to use fuel-efficient vehicles (with a minimum of 45 mpg), or an offer of lower airport fees for operators of clean vehicles (AFVs or other low-emission vehicles). Limousines None of the surveyed airports having clean vehicle policies applied any type of requirement to limousine fleets. Limousine service is a unique market with an exclusive clientele; such services use large luxury vehicles that cannot be converted easily to AF. One survey responder indicated that there are few makes/models of AFVs available that can satisfy the requirements of limousine operations and are reasonably priced. Anecdotally, limo customers value the luxury and size of for-hire vehicles more than the vehicleâs environmental profile. Additionally, an airport is not always the primary market for limousine service. All these factors may contribute to airports choosing not to impose clean vehicle requirements on luxury transportation service providers. Some of the challenges with the availability of AFV models, listed previously, may be related mainly to traditional limousine service that is often associated with vehicles with a lengthened wheelbase (stretch limos) that have a partition between the driver and the passenger and are driven by a chauffeur. Such a narrow definition of limousine service in the current study may give a false impression that there are few opportunities to use AFVs for limousine operations. However, many limo companies also offer executive car/black car service that uses luxury sedans to transport passengers. Unlike traditional limos, there are clean vehicle choices available on the market for black car/executive car service. Black car or executive car service is for-hire transportation that is usually provided in luxury sedans or similar vehicles. Black cars are generally priced midrange between a taxi and a limousine and are often viewed as luxury taxis. Unlike traditional limou- sine service, executive/black cars do not necessarily need advance booking. At some airports, black cars may be available at the curb on a first-comeâfirst-served basis. Call centers for black car companies typically operate as traditional cab services, dispatching vehicles that are currently available. Some executive/black car drivers are dispatched through online ride apps from a mobile device (such as a smartphone), similar to the way TNCs dispatch their vehicles. The use of luxury sedans in black car service allows for the use of AFVs. The market currently offers AFV luxury models that can satisfy the requirements of the executive/black car service. However, anecdotal evidence suggests that, as of this writing, fewer than 1% of the approxi- mately 12,000 executive sedans operating in New York City can be classified as AFVs.
Results 25 Shared Van Rides Shared van rides are traditional and common airport GT operators. Companies offering shared ride service operate in almost all major U.S. airports. An airport is typically a primary market for such operators, warranting a close relationship between them. Some airports choose to manage shared ride operators by including specific requirements in their competitively bid operator agreements. Operators provide service in medium-duty vehicles (mainly vans) that can be converted to AFs. Surveyed airports that choose to impose clean vehicle policies on shared van ride providers are more likely to employ an explicit requirement than any other type of policy. Other policies imposed on these operators include a minimum emission standard for the vehicles and provid- ing incentives in the form of lower airport fees for using AFVs or other clean vehicles. Hotel/Parking Shuttles Not all commercial airports have off-airport parking options, such as shuttle transportation to/from airport parking or hotel shuttles. Hotels located near airports may offer complimentary shuttle service to their clients to and from the airport, but this decision is at the discretion of the hotels. When hotel/parking service is available, it is usually provided in medium-duty or heavy- duty vehicles, such as vans, cutaway buses, or large buses, that can be converted to run on AFs. Surveyed airports that choose to impose clean vehicle requirements on hotel/parking shuttle operators typically employ one of three types of policy: imposing emission standards on vehicles operating at the airport, offering lower airport fees for using AFVs and other clean vehicles, or penalizing with higher fees for not running AFVs or other clean vehicles. Rental Cars Rental car company fleets were outside the scope of the current analysis. Therefore, limited data are available for rental car requirements. Surveyed airports that impose formal clean vehicle requirements on rental car fleets use one of two types of policy: requiring that a certain percent- age of the rental car fleet must be AFVs or offering lower airport fees for using AFVs or other clean vehicles. Rental Car Shuttles Rental car shuttle service provides transportation between airport terminals and a rental car facility, using medium-duty or heavy-duty vehicles, such as cutaway or large transit buses. Such vehicles can be converted to AFVs. This service is typically available at airports where rental cars are located off the property. Therefore, not all airports have such operators or have experience with imposing clean vehicle policies on them. Surveyed airports that choose to impose clean vehicle requirements on rental car shuttle pro- viders employ one of three types of policy: imposing emission standards on vehicles used, offer- ing lower airport fees on vehicles that meet clean vehicle requirements, or imposing penalties in the form of higher fees on vehicles that do not meet clean vehicle requirements. Scheduled Airport Service Scheduled airport service provides regular fixed-route transportation between the airport and one or several off-airport destinations. This service is similar to transit service in an urban area and often employs similar vehicles (large transit buses), which can be converted to run on AFs. Not all airports have scheduled GT service provided by private operators.
26 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Surveyed airports that choose to impose clean vehicle requirements on scheduled airport service providers employ one of three types of policy: imposing emission standards on vehicles used at the airport, offering lower fees for vehicles that meet clean vehicle requirements, or col- lecting higher fees from vehicles that do not meet clean vehicle standards. Transportation Network Companies TNCs, such as Uber, Lyft, and Gett, provide on-demand transportation service similar to taxi- cabs but use individual driversâ noncommercial vehicles. TNCs are partially regulated by the city, county, or state and may have an agreement to pick up and/or drop off passengers at the airport. Airports that sign agreements with TNCs typically require them to implement VMT reduc- tion efforts involving strategies to reduce empty rides. Airports are less likely to impose any restrictions on the types of vehicles used by TNCs, partly because of a large and dynamic pool of vehicles/drivers and partly because of the challenges of enforcement. Surveyed airports that choose to impose clean vehicle requirements on TNCs employ the following three types of policy: offering lower airport fees for vehicles that meet clean vehicle requirements, imposing higher airport fees on vehicles that violate clean vehicle standards, and/or requiring TNCs to implement and document VMT reduction efforts. Airports regularly collect information on the trips by different types of GT operators to track the relative weight of different modes of commercial transportation at the airport. Different airports have different dominant modes, which may affect the airportâs choice of clean vehicle policy. Airports are likely to focus on the most significant GT modes to achieve the maximum desired effect from implementing clean vehicle policies. For example, at some surveyed air- ports, TNC operations account for the majority of GT trips. Not surprisingly, such airports may be more willing to apply clean vehicle requirements to TNCs than are airports with a lower share of TNC operations. Appendix E presents the commercial GT mode split at three surveyed airports. California Air Resources Board (CARB) is developing a strategy to accelerate the deployment of zero-emission transportation services at airports. The goals of this effort include complementing the existing programs focusing on NOx and GHG reduction through the use of zero-emission technologies and increasing the penetration of zero-emission heavy-duty technologies into the airport GT serviceâ airport shuttles, rental car shuttles, parking shuttles, and other types of airport transportation. Since such vehicles are usually used on fixed routes, have stop- and-go operations, maintain low average speeds, and are centrally maintained and fueled, these operations are ideal candidates for zero-emission electric technologies. More information is available at the CARB website (CARB 2017). Airport Clean Vehicle Policies Table 3 summarizes the types of clean vehicle policies that apply to different types of GT providers. Airports may have different motivations for implementing clean vehicle policies and pro- grams, from environmental reasons to business opportunities to increasing AF sales by airport- owned stations. Airports often have multiple motivating factors and pursue multiple goals by implementing clean vehicle programs.
Results 27 The most popular reason for clean vehicle policies (formal or informal) at the surveyed air- ports was to reduce GHG emissions, followed by establishing a green image in the community. Seven surveyed airports with formal or informal policies reported GHG emissions reduction as the reason for implementing the policies. Six surveyed airports with clean vehicle policies consider establishing the airportâs green image as an important reason for implementing the policies. Airports are valuable members of the community. Not surprisingly, they value being viewed as leaders in local environmental initiatives who are engaged in responsible business practices. Three surveyed airports identified complying with government regulations or binding legal agreements as reasons for implementing the policies. Airports are often subject to local environ- mental regulations and standards. For example, an airport that is part of municipal or county government may be subject to clean vehicle requirements that apply to all government fleets. Additionally, some surveyed airports initiate clean vehicle policies to comply with legally binding agreements with state authorities or airport stakeholders. A clean vehicle program at San Diego International Airport (SAN), for example, originated in 2008 as part of a memoran- dum of understanding between the airport authority and the California attorney general. SAN committed to reduce GHG emissions. A Los Angeles International Airport (LAX) policy was mandated by a community benefits agreement between LAX and local community and environ- mental groups to allow the airportâs master plan to go forward. Three surveyed airports view business opportunities as significant motivating factors for implementing clean vehicle policies. All the surveyed airports have alternative fueling infra- structure on airport property. Some airports own AF stations or receive a portion of the proceeds from fuel sales, thereby directly benefiting from increased AFV usage through increased AF sales. Additionally, some airports stated that although they wanted to use AFs in their own fleets, this would not justify the investment in alternative fueling stations if none of the private fleets also used AFVs. Encouraging private fleets to run AFVs allowed airports to convert their own fleets to AFs and justify the infrastructure investment. Figure 13 summarizes the airportsâ major reasons for implementing clean vehicle programs and policies. Airports use different approaches in developing clean vehicle programs. Some involve fleets early in the process and have numerous discussions with affected operators to receive their input and address potential concerns. Others solicit little input from GT fleets during policy develop- ment. Not involving the fleets in policy development might be the result of legal agreements Ground Transportaon Fleet Type AFV Requirement Emission Standard MPG Requirement Lower Fees for Clean Vehicles Higher Fees for Non-compliant Vehicles VMT Reducon Taxicabs Limousines Shared van rides Hotel/parking shules Rental cars Rental car shules Scheduled airport service Transportaon network companies Policy Applies Policy Does NOT Apply Note: Based on the responses from 11 airports. Table 3. Types of clean vehicle policies applicable to different GT operators.
28 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers limiting an airportâs flexibility to negotiate or change policy details. For example, when LAX signed a community benefits agreement with the local community and environmental groups, clean vehicle policy for commercial vehicles was part of the binding legal agreement, leaving no room for negotiations with fleets. Figure 14 shows the breakdown of surveyed airports that do or do not involve private fleets in developing clean vehicle policies. Airports also take different approaches to monitoring and enforcing operator compliance with clean vehicle policies. Some rely on fleetsâ self-certification regarding compliance, whereas others use their own strategies, such as vehicle tracking and inspections. Half of the surveyed commercial service airports that have clean vehicle policies rely on self-certification by the fleets, whereas the remaining half perform monitoring and occasional vehicle inspections themselves or employ third-party consultants. In addition to imposing requirements, airports often offer incentives for complying with policy requirements or disincentives for not complying. Potential incentives may include pref- erential treatment to AFVs through premium parking, offering AF at low or no cost (e.g., electric charging at no additional charge for electricity), providing priority to AFVs to pick up passen- gers at the airport, and lowering fees for complying vehicles. Additionally, airports can charge noncomplying vehicles higher fees (penalty-based policy), reward operators for efforts to reduce empty rides or penalize them for not having effective empty-ride reduction strategies (mainly applies to TNCs), and implement other incentives for encouraging GT operators to comply with clean vehicle policies. 7 6 3 3 2 0 2 4 6 8 Reduce airport GHG emissions Establish âgreenâ image in the community Comply with government regulation/agreement Business opportunity Contribute to carbon accreditation/certification Figure 13. Reasons for implementing clean vehicle policies. 3 2 0 1 2 3 4 Involve Private Fleets Do Not Involve Private Fleets N um be r o f A irp or ts Figure 14. How surveyed airports develop clean vehicle policies.
Results 29 Providing lower airport fees for AFVs appears to be the most popular incentive among the surveyed airports. Three surveyed airports (42.9%) favor this kind of incentive to GT opera- tors. Two surveyed airports offer premium parking for AFVs (e.g., EVs are often allowed to park in the closest spots to the terminal) and provide free vehicle charging for EVs (pay the regular parking fee but not for electricity). Two airports also prefer lowering airport fees for complying vehicles or increasing airport fees for noncomplying vehicles. It is worth noting that disincentives (penalties) for policy noncompliance may be substantial. For example, San Francisco International Airport imposes triple trip fees on courtesy shuttles, hotel/parking shuttles, and some other fleets for not running AFVs. Although the airport technically allows operators to choose what vehicles to use (AFVs are not mandated), GT providers feel they have no choice but to comply with the AFV requirement. From the standpoint of an individual GT operator, a policy with such a severe disincentive is no different from an explicit AFV requirement. Figure 15 summarizes common incentives offered by the airports to private GT providers for complying with clean vehicle policy requirements. Four surveyed airports that employ clean vehicle policies track the environmental impact of the airport sustainability practices, whereas two airports either do not track the impact or are unable to distinguish among specific sources contributing to the overall impact of the airport. Figure 16 illustrates the share of surveyed airports that track the impacts of implemented clean vehicle policies versus those that do not. Survey respondents indicated that accurate tracking of the impacts of clean vehicle policies is essential to ensuring that the program goals are achieved in the most efficient way. Four surveyed airports (50%) listed a lack of financial resources or government grants as a major barrier to implementing clean vehicle policies. The state of AF technology, including the availability of vehicles with the required characteristics, fast changes in AF technologies that necessitate regular updates of policy requirements, and other factors were reported as major barriers. The higher up-front costs of AF technologies that make them not competitive with tra- ditional propulsion technologies were also considered a major obstacle to implementing clean vehicle programs. Other potential barriers included the following: ⢠Lack of understanding and prioritization of emission reduction efforts from private fleets; ⢠Lack of public-use alternative fueling infrastructure; ⢠Difficulty with monitoring and enforcement of clean vehicle policies; ⢠Being out of phase with the concession negotiation timeline; ⢠Ensuring that a proposed policy provides fair treatment to all affected fleets; and 3 2 1 2 2 2 1 0 1 2 3 4 Lower airport fees for AFV Premium parking for AFV Priority to pick up passengers Higher airport fees for non-AFV Free charging for EVs Lower airport fees for reducing VMT (TNC) Higher fees for not reducing empty rides (TNC) Figure 15. Incentives for complying with clean vehicle policies. Track 4 Do Not Track 2 Figure 16. Airports tracking impacts of clean vehicle policies.
30 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers ⢠The impact of TNCs on GT operators limiting the ability of airports to impose additional regulations/requirements on an already struggling industry. At the same time, two surveyed airports see no obstacles/barriers for implementing clean vehicle policies. Figure 17 summarizes the major barriers perceived by the surveyed airports. The surveyed airports were asked to identify key factors that are critical for the success of clean vehicle programs. Partnerships with fleets and fuel suppliers to ensure cooperation and operator access to fuel was cited as a major success factor by six surveyed airports (85.7% of respondents). Five airports (71.4%) said that airport leadership is critical. About half named the availability of government grants or private funding for AFV acquisitions and conversions as an important success factor. Other success factors included political will, clear understanding of the policy scope and the types of fleets it will apply to, implementing an effective tracking system for enforcing fleet compliance, introducing competition, and approaching the policy from a busi- ness perspective. Figure 18 summarizes the major success factors for implementing clean vehicle policies reported by the surveyed commercial service airports. Four surveyed airports that have clean vehicle policies are at least somewhat satisfied with their policy, and one airport is dissatisfied. Figure 19 summarizes airport satisfaction level with the existing policies. 1 3 3 1 4 1 1 1 1 2 0 1 2 3 4 5 Lack of understanding/prioritization from fleets State of alternative fuel technologies Cost of AFV Lack of public fueling infrastructure Lack of financial resources/grants for AFV Difficulty with monitoring/enforcement Out of phase with concession negotiation timeline TNC impact on the industry Providing fair treatment to all fleets None Figure 17. Major barriers for implementing airport clean vehicle policies. 5 1 3 6 1 1 1 0 1 2 3 4 5 6 7 Airport leadership and initiative Political will Availability of funding Partnership with fleets and fuel suppliers Clear determination what fleets will be covered Have tracking system and enforcement mechanism Introduce competition/business approach Figure 18. Major success factors for implementing clean vehicle programs. Mostly dissatisfied 1 Fairly satisfied 1 Mostly satisfied 3 Figure 19. Airportsâ satisfaction with existing clean vehicle policies.
Results 31 Anti-idling Policies Three of 11 surveyed airports reported having an explicit anti-idling policy, whereas five airports did not have an airport-specific policy against vehicle idling. All the airports that did not impose airport anti-idling requirements had active anti-idling policies imposed by the state, county, or municipal governments, and there was no need for a separate airport-specific requirement. Additionally, three surveyed airports employ anti-staging rules and/or loading zone time limits. Such strategies indirectly reduce vehicle idling because they limit the amount of time that passenger-loading vehicles can remain stationary at the curb. Figure 20 demonstrates the shares of airports with and without explicit anti-idling policies. Two of the surveyed three airports that have anti-idling regulations prohibit any idling at the airport, whereas one surveyed airport restricts vehicle idling to 5 min. These idling rules are enforced by airport personnel. Figure 21 summarizes the details of idling restrictions at airports with idling policies. Airports that do not have their own idling policies rely on state or local government policies enforced by state or county law enforcement. In most cases, government regulations restricted idling to 5 min, but a 3-min idling restriction was reported by one location. Figure 22 provides details about state or local government idling regulations at surveyed airports lacking their own anti-idling policies. Airport idling policy 3 No airport idling policy 5 Anti-staging policy/loading zone limit 3 Figure 20. Anti-idling policies. 2 1 0 1 2 3 No Idling 5 Min of Idling N um be r o f A irp or ts Figure 21. Airport idling restrictions.
32 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Funding for Fleet Conversion to AFVs Government grants and rebates covering the incremental cost of acquisition or conversion of AFVs are essential for encouraging GT fleets to adopt AFV technologies. Six of the 11 surveyed airports are aware of existing government grants that help fleets convert to AFVs or have taken advantage of such grants. Five airports reported not being aware of any existing government grants for AFV conversions. The lack of knowledge about grant availability does not necessar- ily mean there are no relevant government grants but rather reflects a subjective opinion of the surveyed airport. The grants supporting airport clean vehicle conversions listed by the surveyed airports include state grants funded by state-imposed fees/taxes (these were mainly available in California); Diesel Emissions Reduction Act (DERA) grants; potential grants originating from the VW settle- ment proceeds to states; and other grants. Although the surveyed airports mentioned potential VW settlement funds, there are currently no established grant programs for airport clean vehicle conversions funded by VW settlement proceeds. Private GT providers have access to an even smaller pool of potential grant funding opportuni- ties to finance fleet conversions to AFVs or other clean vehicles. Seven of the 11 surveyed airports indicated there were currently no grants available to private fleets to convert to AFVs. Additionally, two airports stated that they were unaware of any available grants for AFVs applicable to private fleets. The few grants that were identified included potential VW settlement funds (mentioned by one airport), unnamed state grants, and a voucher program lowering the cost of AFV acquisi- tion (available mainly in California). Voucher programs are designed by states to streamline AFV acquisition by shifting the burden of the grant application process from fleets to vehicle dealers. Voucher programs can be funded by various sources, including the CMAQ program. Airports also mentioned that in the past there were more state grants and rebates for AFVs than are currently available because such grants have been discontinued. One example is Floridaâs Natural Gas Fuel Fleet Vehicle Rebate offered by the state since 2013. The rebate program provided 50% of the incremental cost of the acquisition of natural gas vehicles by private and public fleets. In 2017, the Florida legislature discontinued this rebate, and there is currently no funding available for fiscal year 2017â2018. Figure 23 shows the types of grant funding available to private GT fleets for AFV acquisition and conversion. Three surveyed airports said the available grants are being highly utilized by the airports and fleets. One airport indicated an inability to apply for grants because most of the funds in the available programs were already committed for several funding cycles. 4 1 0 1 2 3 4 5 5 Min of Idling 3 Min of Idling N um be r o f A irp or ts Figure 22. Government anti-idling regulations for airports without idling policies.
Results 33 Eight of the 11 surveyed airports stated they are unable to help private GT providers receive government grants for converting their fleets to AFVs. Only one airport reported that it does help private airport operators with securing funding for fleet conversion to clean vehicles. Figure 24 summarizes the assistance of the surveyed airports with obtaining grant funding for private GT operators. Transportation Network Companies at the Airports All 11 surveyed airports allow transportation network companies to operate at the airport with varying levels of regulations and oversight. Three airports that have clean vehicle policies do not require TNCs to comply with airport clean vehicle policies. Two airports provide incen- tives to TNCs in the form of reduced fees for using AFVs at the airport and for implementing strategies to reduce empty rides. One airport applies a penalty-based policy to TNCs for not complying with fuel efficiency requirements. Seattle International Airport charges TNCs double the normal trip fee for fleets that fail to meet airport environmental key performance indica- tors. Appendix D provides an example of an operating agreement used by Seattle International Airport with TNCs. Figure 25 summarizes the types of clean vehicle policies that apply to TNCs operating at the surveyed airports. 1 1 1 2 7 0 1 2 3 4 5 6 7 8 State grants Voucher program VW Settlement Funds (Potentially) Unknown None Figure 23. Grants available to private GT providers. Airport does NOT help with grants 8 Airport sometimes helps with grants 1 Unable to help currently, but used to help in the past 1 Airport helps secure grant/funding 1 Figure 24. Grant assistance by airports to private operators.
34 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Contacted airports voiced several concerns and challenges related to TNC operations. Airports admitted that regulations for TNCs are still under development, allowing TNCs to enjoy an advanta- geous position compared with other GT operators. In some cases, airports are unable to apply clean vehicle policies to TNCs because of light state regulation of TNCs. Finally, because of a large number of vehicles and driver turnover, TNCs do not provide vehicle lists and/or driver information to airports, making it a challenge to track their operations. Airports have to rely on the data provided by TNCs and work with them to establish a geofenced staging area for airport trips. Despite these challenges, airports recognize that they have the responsibility to manage ground access that allows many GT services and business models, including TNCs, to be available for the traveling public. In summary, airport transportation services are in a period of transition, with new business models changing the market landscape. Although TNCs are offering low-cost transportation services, these operators are not currently profitable, and new approaches and strategies are likely to emerge in the near future. It is not clear yet what the outcome will be of these changes or how they will affect the airport GT landscape. Ground Transportation Providersâ Perspective General Fleet Information Thirteen different private GT fleets were interviewed regarding their experiences with airport-imposed clean vehicle policies. Surveyed fleets include taxicabs, limousine service provid- ers, shared van rides, parking shuttles, rental car shuttles, scheduled airport service, and TNCs. Eight of the 13 surveyed private fleets operate at airports that were also surveyed for this study, whereas five surveyed fleets come from other commercial service airports. Table 4 provides a list of the types of private fleets surveyed for this study. The size of the fleet is an important factor in the decision to convert vehicles to AFs. Converting larger fleets with more vehicles is typically more difficult (expensive) and may require more time. Additionally, the vehicle ownership model affects the ability and willingness of GT operators to implement clean vehicle policies. Fleets that own (or lease) their vehicles have more control over the types of vehicles used than do fleets that mostly use owner-operators or a hybrid ownership model, in which the company owns only part of the fleet while owner-operators own another part. 3 2 1 TNCs are not subject to policy Reduced airport fees for AFV use, empty rides reduction Higher airport fees for fuel-inefficient vehicles Figure 25. Types of clean vehicle policies that apply to TNCs.
Results 35 The data from the surveyed GT fleets indicate that smaller fleets are more likely to use company- owned vehicles, whereas larger fleets prefer owner-operator or hybrid vehicle ownership models. Surveyed GT operators consist of fleet sizes ranging from 10 to 405 vehicles. The average fleet size of the surveyed providers is 98 vehicles. The size of the vehicle fleet serving the airport market and vehicle ownership models for the surveyed GT operators are summarized in Appendix F. Not all surveyed operators run alternative fuel or other clean technology vehicles at their air- port operations. The percentage of AFVs serving the airport market ranges from 0% to 100%. On average, over half of the surveyed fleetsâ vehicles serving the airport are AFVs or hybrids. Ground transportation operators that choose to employ AFVs and other clean vehicles mainly prefer CNG, hybrid-electric, and electric vehicles. Five surveyed private fleets using AFVs and other clean vehicles in their airport operations reported using CNG vehicles. Four surveyed pri- vate GT fleets (44.4% of fleets using AFVs) employ hybrid-electric technologies, and three fleets use EVs. Surveyed GT fleets also employ propane vehicles (both dedicated and bi-fuel), biodiesel, and PHEVs. Figure 26 summarizes the types of clean vehicles operated by the surveyed GT fleets. Alternative fuel vehicles vary in the environmental benefits they can provide compared with vehicles using traditional fuels. Natural gas and electric vehicles typically have the highest emission reduction potential among the AF technologies available on the market. Appendix G summarizes the comparison of emissions from common types of AFs used in different types of vehicles. Fleet Type Number of Operators Surveyed Taxi 3 Limousine 2 Shared van ride 3 Parking shuttle 2 Rental car shuttle 1 Scheduled airport service 1 Transportation network company 1 Total 13 Table 4. Types of GT fleets surveyed. CN G EV PH EV Pro pa ne (D ed ica ted ) Pro pa ne (B i-fu el) Hy bri d-e lec tri c Bio die sel 5 1 1 4 3 1 1N um be r o f S ur ve ye d Fl ee ts Figure 26. Types of AFVs and clean vehicles operated by surveyed fleets.
36 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Seven of the 13 surveyed GT companies (53.8% of the survey sample) own the vehicles they operate, and three surveyed fleets use an owner-operator model, in which all the vehicles are owned by drivers contracted by the company to provide service. Additionally, three surveyed operators reported using a hybrid ownership model, in which a company owns a portion of the fleet (usually less than 50%) while another portion is owned by individual operators. Figure 27 summarizes vehicle ownership models for the surveyed GT fleets. Different types of fleets vary in the type of ownership model preferred. Taxicabs are more likely to be operated by drivers owning their own vehicles than are other types of GT fleets, excluding TNCs. Two of the three taxicab companies surveyed for this study do not own most of the vehi- cles but use a hybrid ownership model, in which the company owns only a small portion of the overall fleet and most of the vehicles are operated by vehicle owners. Of the two surveyed limousine operators, one company owned the vehicles and another used owner-operators. Figure 28 and Figure 29 summarize vehicle ownership models for the surveyed taxicab and limousine companies, respectively. The vehicle ownership model can affect the implementation of clean vehicle policies because it affects the level of control a company has over the types of vehicles used. For example, GT operators that predominantly use owner-operators have less flexibility in Company- owned 7Owner- operators 3 Hybrid ownership 3 Figure 27. Vehicle models owned by surveyed fleets. Company- owned 1 Hybrid ownership 2 Figure 28. Vehicle models owned by surveyed taxicab operators.
Results 37 implementing clean vehicle programs because the decisions regarding the types of vehicles and fuels used are made by vehicle owners (individual drivers) rather than the taxi company. GT operators that own their vehicles are better suited for implementing clean vehicle policies and other sustainability initiatives. Ground transportation emissions at the airport are affected by multiple factors, including GT mode split, number and types of vehicles used, number of trips, and trip length. Designing an effective clean vehicle policy requires accounting for these multiple factors and involves balancing the interests of the parties involved and/or affected by the policy. Despite these complexities, any GT mode that uses high-occupancy vehicles (e.g., shared van ride, parking shuttle, hotel shuttle, transit) provides a clear environmental benefit over private pickups and drop-offs at the airport. Therefore, any airport policy that draws airport customers toward GT modes with multiple passengers per vehicle is environmentally superior to private automobiles. Types of Current Sustainability Practices All surveyed fleets use some sort of sustainability practices while operating at the airport, including the use of AFVs, idle reduction efforts, the use of fuel-efficient and low-emission vehicles, and strategies for reducing deadhead trips. The use of AFVs and idle reduction poli- cies are the two most popular sustainability strategies for the surveyed GT fleets. Eight of the 13 surveyed operators (61.5% of the survey sample) employ AFVs in their fleets operating at the airport, whereas four operators (30.8% of the survey sample) employ idle reduction policies. Three surveyed operators implement deadhead trip reduction strategies. The same number of operators rely on fuel-efficient vehicles and/or newer model vehicles for their airport trips. Figure 30 summarizes the types of sustainability practices employed by the surveyed GT fleets while operating at the airports. Surveyed fleets often employ more than one type of sustainability practice, resulting in the cumulative number of sustainability strategies exceeding the total number of surveyed fleets. Company- owned 1 Owner- operators 1 Figure 29. Vehicle models owned by surveyed limousine operators.
38 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers The most popular deadhead trip reduction strategies include matching drop-offs with pickups at the airport and adjusting the type and size of vehicles for specific tasks to reduce empty seats. Operators can be penalized with higher trip fees if they do not follow the deadhead trip reduction strategies required by their agreement. Although some operators said it may not always be fea- sible to pick up a paying customer on the way to the airport, especially in the case of short trips, GT providers operating at Seattle International Airport (SEA) can receive preferential treatment if they demonstrate a successful empty ride reduction strategy. Although there are some similarities between airports and private fleets in the motivation for implementing clean vehicle policies, GT fleets have slightly different reasons for adopting sustain- ability practices. Aside from environmental reasons, private fleets often look at AF technologies from an economic standpoint (i.e., as a way to save money). Six surveyed GT fleets (54.5% of responders) reported the desire to reduce emissions and the environmental impact of the fleet as the major reason for adopting AFVs or other sustainability practices. Four surveyed fleets (36.4% of responders) implemented AF technologies to save on operating costs (including fuel and maintenance costs). The same number of surveyed fleets implemented sustainability prac- tices to comply with airport policy requirements (either an explicit requirement or a significant penalty imposed by the airport). One surveyed operator also mentioned the desire to provide the most efficient experience for customers as a motivating factor for implementing fleet sustain- ability practices. Figure 31 summarizes the primary reasons for the surveyed fleets to implement sustainability practices on vehicles serving the airports. 8 4 3 3 AFV Idle Reduction Fuel-efficient and Newer Models Deadhead Trip Reduction Figure 30. Sustainability practices of surveyed GT fleets. 4 6 4 1 Cost Savings Reduce Emission/Environmental Impact Airport Requirement Create Efficient Experience for Customers Figure 31. Reasons GT fleets implement sustainability practices.
Results 39 Other potential reasons for considering sustainability practices or adopting AFVs men- tioned by the surveyed fleets included separating themselves from the competition and fol- lowing companywide policies involving AFV adoption in all locations where the company operates. Groome Transportation is a private shuttle service provider operating in the southeast United States with offices in Athens, Georgia; Auburn, Alabama; Augusta, Georgia; Chattanooga, Tennessee; Columbus, Georgia; Macon, Georgia; and Warner Robbins, Georgia. The company provides shuttle transportation to and from Hartsfield-Jackson Atlanta International Airport (ATL), Nashville International Airport (BNA), colleges, universities, and military bases in the southeast, as well as group charter transportation services in Georgia, Alabama, and Tennessee. Groome Transportation operates propane- powered vehicles in all of its locations and says that propane is better suited overall than traditional fuels (gasoline or diesel) for GT providers that offer long-distance regional service. The use of propane-powered vehicles allows the company to realize fuel cost savings, lower the frequency and cost of engine repairs (because propane burns more cleanly than gasoline or diesel), and run environmentally friendly operations. Future Sustainability Plans Seven surveyed GT fleets (70% of responders) reported plans to continue or expand the use of their current AF technologies. This includes the use of CNG, propane (dedicated and bi-fuel), and hybrid vehicles. Three fleets indicated they might consider other AFVs or tech- nologies in the future if their technical characteristics, costs, and return on investment (ROI) parameters improve. Other plans included implementing a more-effective system to track empty rides and implementing an EV leasing program. Two surveyed GT fleets reported no plans to implement additional sustainability practices. However, different operators pro- vided different reasoning for the lack of plans. One operator was happy with existing prac- tices, whereas another indicated being in a survival mode and not in a position to invest in AFVs in the near future. Figure 32 summarizes plans of the surveyed fleets for implementing environmental initiatives. Two surveyed fleets consider the availability of vehicles that can meet company needs as a major challenge for implementing future sustainable initiatives. This refers to the lack of AFVs that can satisfy fleet requirements or lack of certified vehicles that can be converted to AFs. Two other surveyed fleets view the state of AF technologies as the major obstacle for implementing sustainability initiatives in the future. The state of AF technologies refers to the multiple charac- teristics of AFVs that make them practical and competitive with traditional vehicles, including vehicle fuel economy, driving range, refueling time, and cargo space. Other potential challenges with future AF projects include access to fuel, customer acceptance of AFVs, and the price differential between alternative fuel and traditional vehicles. Anecdotal evidence also suggests that a prolonged period of low gasoline and diesel prices is largely respon- sible for a slowdown in the adoption of clean fuel technologies in the past few years. Figure 33 summarizes the challenges identified by the surveyed fleets for implementing planned sustain- able initiatives.
40 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers 7 3 1 1 2 0 1 2 3 4 5 6 7 8 Continue/Expand Using Current AF Technology May Consider Other AF Technologies/Vehicles Implement Better Vehicle/Trip Tracking System Implement AFV Lease Program None Figure 32. Future sustainability initiatives planned by surveyed fleets. 1 2 1 2 1 0 1 2 3 Access to fuel Availability of vehicles meeting company needs Customer acceptance of AFVs State of AF technologies Price differential between alternative and traditional fuels Figure 33. Main challenges with implementing planned sustainable initiatives.
Results 41 WallyPark, an off-airport parking provider serving multiple locations around major U.S. airports, is now offering a ride between Los Angeles International Airport (LAX) and its off-airport parking facility using all-electric shuttle buses. WallyPark purchased 16 zero emissions utility shuttle (ZEUS) buses from Phoenix Motor Cars (California-based EV developer) to serve the LAX market. Each of the 14-passenger shuttles is expected to reduce GHG emissions by more than 60 tons of carbon dioxide per year compared with similar diesel vehicles. The shuttles run 4-mi round trips between the WallyPark parking location and LAX terminals, and they can be fully recharged in less than 3 h. This is the first all-electric, off-airport parking shuttle service in the country, and WallyPark is planning to add electric shuttle service at other major U.S. airports in the near future (Hall 2017). Airport Clean Vehicle Policies Nine of the 13 surveyed fleets (69.2%) operate at airports that do not impose clean vehicle policies on private GT operators; only four surveyed GT fleets are subject to airport-imposed clean vehicle policies and programs. Interview discussions with GT providers revealed the following five types of clean vehicle requirements imposed by the airports on private operators: 1. GT vehicles operated at the airport must have fuel economy of 41 mpg or higher (typically applies to taxis). 2. Operators must implement deadhead reduction strategies (typically applies to TNCs). 3. All trips made by operators in the vehicles that are not comparable to AFVs in terms of emissions are subject to triple airport trip fees. 4. Operators must use AFVs or AFV-comparable emission vehicles at the airport. 5. Twenty-five percent of taxi fares from the airport should be made on clean air vehicles. These policies are formalized by including clean vehicle requirements in contracts and concession agreements with operators, as well as in airport rules and regulations. Policy types 3 and 4 are somewhat similar. The key difference between these two types is that one imposes an explicit requirement to use AFV-comparable vehicles, whereas the other penalizes for not using such vehicles. Although there is no mandated requirement to use AFV-comparable vehicles, surveyed operators say they have no choice but to comply because of a severe penalty (double or triple trip fee). Thus, this penalty-based policy effectively works as an explicit AFV requirement. Two surveyed operators that are subject to airport-imposed clean vehicle policies reported that the airports had not involved the affected GT fleets in developing the policy, whereas one surveyed operator indicated that the airport solicited private fleet input for developing clean vehicle requirements. Figure 34 illustrates the involvement of the surveyed fleets in the develop- ment of airport clean vehicle policies. Three of the surveyed fleets that are subject to airport-imposed clean vehicle programs stated that although they encountered resistance from their employees at the early stages of policy implementation, most company employees embraced the policy after experiencing AFV tech- nologies in action. However, one surveyed fleet indicated drivers were still unhappy with some
42 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers aspects of the airport-imposed clean vehicle policies. The attitudes of the private fleetsâ vehicle drivers about airport clean vehicle requirements are graphically presented in Figure 35. The main reasons for the initial pushback from the drivers included concerns about the cost of vehicle conversions and doubts regarding the ability of clean vehicles to satisfy operator service requirements. These concerns were mostly addressed after the drivers had the opportunity to experience AFVs and test their capabilities. Six surveyed fleets (two-thirds of the responders) experienced difficulties in meeting the requirements of the airportâs clean vehicle policies, and two surveyed operators found compli- ance to be difficult. Three surveyed GT operators were able to meet the requirements with no difficulties. Figure 36 summarizes the difficulty level of complying with airport clean vehicle policies as perceived by the affected private fleets. A lack of appropriate AFVs that can satisfy service requirements is a common difficulty expe- rienced by operators while working on their compliance with airport clean vehicle requirements. Two surveyed operators listed availability of appropriate AFVs or vehicles suitable for AFV con- version as the main difficulty when the policy was initiated. Other challenges mentioned by the surveyed operators include extensive reporting required for documenting empty ride reduction, up-front costs of AFVs, and a lack of qualified/certified mechanics to service AFVs. Figure 37 summarizes the main difficulties encountered by the surveyed fleets in meeting airport clean vehicle requirements. Two surveyed GT operators (half of the responders) said that the clean vehicle policies imple- mented by the airports are at least somewhat successful, but the other two responding fleets are 1 2 Airports involved fleets in developing policy Airports did NOT involve fleets in developing policy Figure 34. GT operatorsâ involvement in developing clean vehicle policies. 3 1 0 1 2 3 4 Initial resistance, but now embrace existing practices Drivers unhappy with some aspects of policy Figure 35. Driver acceptance of clean vehicle requirements. Not difficult/Easy 3 Somewhat difficult 4 Very difficult 2 Figure 36. Difficulty level of complying with clean vehicle requirements.
Results 43 unable to evaluate the success because the original specific goals of the implemented programs are unknown to the surveyed fleets. Barriers and Incentives More generally, the main barriers that GT providers encounter while implementing different kinds of sustainability projects are directly related to AFV characteristics and limitations or access to fuel. Five surveyed operators (45.5% of the responders) consider the higher up-front cost of AFVs as the major barrier to adopting AF technologies. Four surveyed fleets view range and fuel- ing time of AFVs as the main barriers for AFV adoption, whereas three operators reported access to alternative fueling infrastructure as a barrier to implementing sustainability projects. Other potential challenges mentioned by the surveyed operators include regulatory rules and restric- tions for AFV conversions, a lack of qualified/certified mechanics to service AFVs, the low price of gas making investment in AFVs more difficult to justify, the availability of AFVs that meet fleet service requirements, and customer preference toward larger rather than fuel-efficient vehicles. Although most of the listed challenges were not specific to any particular AFV technology, some GT fleets operating EVs noted the degradation of vehicle battery performance under cold climate conditions reducing vehicle range. It is common for EVs to have lower usable range under extreme cold conditions compared with hot weather. GT fleets that operate EVs in cold climates may find battery sensitivity to climate conditions somewhat problematic. Figure 38 summarizes the major barriers for implementing sustainability projects by GT providers. 1 2 1 1 0 1 2 3 Documenting empty rides reduction requires extensive reporting Availability of appropriate vehicles Costs of AFVs Lack of qualified mechanics Figure 37. Main difficulties fleets face in meeting clean vehicle requirements. 1 2 2 1 5 4 3 1 0 2 4 6 Regulatory issues regarding AFV conversions Lack of qualified/certified mechanics Low price of gas Availability of AFVs Higher upfront costs of AFVs Range and fueling time of AFVs Access to alternative fuel infrastructure Customersâ preferences Figure 38. Barriers GT fleets face in implementing sustainability practices.
44 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Certain strategies implemented by fleets can mitigate some (but not all) of these barriers. For example, fleets can employ bi-fuel vehicles that can run on both an alternative and regular fuel. An operator can then decide whether to run the fleet on regular or alternative fuel depending on the existing fuel price differential. Developing or hiring in-house specialists to maintain AFVs can help fleets overcome the shortage of AFV mechanics. Surveyed fleets reported three types of incentives that are currently available to GT operators for implementing sustainability projects at the airports: 1. Federal, state, or local tax credits/rebates for purchasing AFVs (mainly referring to federal $2,500â$7,500 rebate for the purchase of plug-in EVs). 2. Grants and rebates to purchase and convert AFVs (these are typically provided by states and cover a portion of incremental costs of acquiring/converting AFVs). 3. Lower airport trip fees for AFVs and low-emission vehicles (offered by airports as part of the clean vehicle policies). Five surveyed GT fleets (41.7% of responders) were aware of the federal/state/local tax credits for AFVs, and three operators listed grants and rebates for purchasing AFVs as available incen- tives for implementing sustainability projects. Three surveyed GT operators (25% of responders) stated there are currently no incentives available to private fleets for funding clean vehicle proj- ects. Two other private fleets were not aware of any existing government incentive for AFVs and other clean vehicles. Figure 39 lists available incentives for implementing sustainability projects as reported by the surveyed fleets. Surveyed fleets find government tax credits and rebates, as well as preferential treatment of AFVs by the airports, as the most effective incentives for encouraging GT operators to adopt AFVs and other sustainability practices. Four surveyed fleets (36.4% of the responders) con- sider government tax credits and rebates as one of the most effective incentives. The same number of operators also consider preferential treatment by the airports, such as providing prime locations to AFV operators to pick up/drop off passengers, offering lower airport trip fees, and so forth, as the most effective types of incentives for encouraging investment in clean vehicles. Direct grants to purchase AFVs and offering longer airport agreements (with exclu- sive airport access) to operators running AFVs were both named as the most effective types of incentives by three surveyed fleets. Figure 40 summarizes AFV incentives that the surveyed GT providers find most effective. 1 2 3 3 5 0 1 2 3 4 5 6 Lower airport trip fees for AFVs and low- emission vehicles Not aware of any incentives None Grants/rebates to purchase/convert AFVs Federal, state, or local tax credits/rebates for purchasing AFVs Figure 39. Types of incentives available to GT fleets.
Results 45 Fleetsâ Recommendations During the interviews, surveyed fleets provided their recommendations for designing effective airport clean vehicle policies. The suggestions ranged from vague recommendations to specific proposals. The suggestions cited most often included ensuring fleet access to fuel by providing fueling infrastructure at the airport (six surveyed fleets, or 50% of the responders), involving GT providers in the development of clean vehicle policies (three fleets), and treating all operators equally/fairly (three fleets). Two surveyed GT fleets suggested airports offer longer and/or exclu- sive contracts with operators that implement AFVs to allow adequate time for them to recoup the investment. Other suggestions included revising deadhead reduction requirements to elimi- nate applicability to shorter trips and considering creative approaches to increase the pool of AFVs rather than restrict the types of vehicles at the airport. Figure 41 provides a summary of the suggestions by the surveyed fleets regarding designing successful airport clean vehicle policies. 1 1 3 3 4 4 0 1 2 3 4 5 Incentives addressing long-term issues of AFVs More alternative fueling infrastructure at the airport Direct grants to purchase/convert AFVs Longer airport agreement and exclusive airport access Tax credits and rebates Preferential treatment of AFV by airport Figure 40. Incentives found most effective by surveyed fleets. 6 3 2 1 1 1 3 1 0 1 2 3 4 5 6 7 Ensure fleetsâ access to fuel/provide fueling infrastructure Involve GT providers while developing clean vehicle policy Longer/exclusive contracts with GT providers using AFVs Ensure consistency between policy and local regulations Revise deadhead reduction requirements for short trips Stimulate AFV usage rather than restrict traditional vehicle use Treat all operators fairly Clear and concise policy that makes economic sense to fleets Figure 41. Recommendations to airports on designing clean vehicle policies.
46 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Transportation Network Companiesâ Market Impact Most of the operators surveyed for this study indicated they were directly or indirectly affected by TNC operations at the airports. Traditional GT providers (especially taxicabs) reported experiencing significant loss in market share to TNCs. Figure 42 summarizes the impact of TNC operations at the airports on the surveyed GT providers (excluding TNCs). Common suggestions provided by the surveyed GT operators to the airports regarding TNCs include the following three topics: 1. EquityâAirports should treat all operators equally, make everyone pay the same fees, and provide the same access to the airport. 2. Traditional OperatorsâAirport policy toward TNCs is not helping traditional operators. TNCs face few requirements and enjoy an advantageous position compared with traditional operators that cannot adopt the same business model. 3. RegulationsâAirports should not impose any more requirements on a taxicab industry that is already struggling because of competition with TNCs. Summary of Practices and Lessons Learned Airports ⢠All surveyed airports use and/or encourage one or more sustainability practices to reduce emissions. The most popular sustainability strategies include the use of AFVs (nine sur- veyed airports, 81.8% of responders), restrictions for vehicle idling (five airports, 45.5% of responders), the use or encouragement of fuel-efficient and low-emission vehicles such as hybrids (three airports, 27.3%), encouragement of private GT operators to implement strategies that reduce empty rides (three airports, 27.3%). ⢠All surveyed airports encourage the use of AFVs at the airport through formal or informal policies. Even airports that actively use AFs in their own fleets are not always willing to require private GT operators to use AFVs at the airport. ⢠CNG, propane, and electric vehicles appear to be the most popular AF technologies at surveyed airports. Airport-owned fleets operate vehicles using CNG (10 surveyed airports, 90.9% of responders), propane (five airports, 45.5%), and electricity (six airports, 54.5%). Airports also encourage private operators to use these fuels more often than other AFs. ⢠Six of the 11 surveyed airports (55% of the survey sample) have a formal clean vehicle policy that applies to private GT providers; five airports (45%) have no formal policy. Additionally, two airports have informal clean vehicle policies for private operators. Loss of market share 5 Practically no effect 1 Figure 42. Impact of TNCs on traditional GT operators.
Results 47 ⢠Common types of clean vehicle policies: 1. Explicit requirement for AFV use (used by three surveyed airports with formal policies). 2. Fuel-emission standards (one airport). 3. Minimum vehicle fuel economy requirement (one airport). 4. Incentive for using AFVs in the form of lower airport fees (one airport). 5. Penalty for not using AFVs in the form of higher airport fees (two airports, 33.3%). 6. Requirements for GT operators to reduce empty rides (three airports, 50%). ⢠Airports are aware that when they do not impose explicit requirements but use severe penalties for not using AFVs (e.g., triple airport trip fees), operators often feel they do not have a choice but to comply with the AFV suggestion. ⢠Different types of clean vehicle policies may apply to different types of GT providers: 1. Taxicabsâtypically subject to three types of policies: an explicit requirement for the use of AFVs, a requirement to use fuel-efficient vehicles (with a minimum of 45 mpg), or offering lower airport fees for running clean vehicles (AFVs or low-emission vehicles). 2. Limousinesâtypically are not subject to airport clean vehicle policies. 3. Shared van ridesâmostly subject to explicit AFV requirements, minimum emission stan- dards, and incentives in the form of lower airport fees for using AFVs. 4. Hotel/parking shuttlesâtypically subject to emission standards, lower airport fees for using AFVs, and penalties in the form of higher airport fees for not running AFVs. 5. Rental car shuttlesâtypically subject to emission standards, lower airport fees for meet- ing clean vehicle requirements, or penalties in the form of higher airport fees for not meeting clean vehicle requirements. 6. Scheduled airport serviceâtypically subject to emission standards, lower fees for meeting airport clean vehicle requirements, or higher airport fees for not meeting clean vehicle standards. 7. Transportation network companiesâsubject to light requirements by local jurisdictions and the airports. Airports typically require TNCs to implement VMT reduction efforts (reduction of empty rides). ⢠Main reasons for implementing clean vehicle policies by airports: reduce emissions (seven surveyed airports, 87.5% of responders), establish green image in the community (six airports, 75.0%), comply with government regulations (three airports, 37.5%), business opportunity (three airports, 37.5%), and contribute to carbon accreditation (two airports, 25.0%). ⢠Three surveyed airports (60% of the responders with clean vehicle policies) involve GT opera- tors in the development of clean vehicle programs. ⢠Common AFV incentives offered by airports to GT operators: lower airport fees (three surveyed airports, 42.9% of the responders), premium parking for AFVs (two airports, 28.6%), priority for picking up passengers (one airport), higher airport fees for non-AFVs (two airports, 28.6%), free charging for EVs (two airports, 28.6%), lower airport fees for VMT reduction (two airports, 28.6%), and higher airport fees for not reducing empty rides (one airport). ⢠Major barriers for implementing airport clean vehicle programs: lack of financial resources/ grants to acquire AFVs (four surveyed airports, 50.0% of the responders), state of AF tech- nologies (three airports, 37.5%), and costs of AFVs (three airports, 37.5%). ⢠Four surveyed airports (80% of the responders) are satisfied with existing clean vehicle policy. ⢠Three airports (half of surveyed airports with clean vehicle policies) do not apply clean vehicle policies to TNCs. ⢠Challenges/concerns related to TNCs operating at airports: 1. Regulations for TNCs are still under development; TNCs often enjoy an advantageous position compared with other GT operators. 2. Airports are unable to apply clean vehicle policy to TNCs because of light state regulation of TNCs. 3. Due to the large number of vehicles and driver turnover, TNCs do not provide vehicle lists and/or driver information to airports, making it a challenge to track their operations. Airports have to rely on the data provided by TNCs.
48 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers Private Fleet Operators ⢠Fleets have a slightly different perspective on AFV requirements than do airports. Fleet decisions are often dominated by the economics of AFVs (life-cycle costs, ROI, ways to save money), regulations, business needs, and customer preferences. The main reasons for implementing sus- tainability practices by fleets are as follows: reduce emission/environmental impact (six surveyed fleets, 54.5% of responders), cost savings (four fleets, 36.4%), and comply with airport clean vehicle requirements (four fleets, 36.4%). ⢠CNG, hybrid-electric, and electric vehicles are the most dominant clean vehicle technologies used by private GT operators. These technologies are used by five, four, and three surveyed private fleets, respectively. ⢠Eight surveyed fleets (61.5% of the surveys sample) own their own vehicles, whereas five fleets (38.5%) use driver-owned vehicles. ⢠Use of AFVs and idle reduction practices are the most popular sustainability activities by surveyed fleets. Eight surveyed operators employ AFVs in their fleets operating at the air- port, whereas four surveyed fleets (30.8%) employ idle reduction policies. Many fleets employ more than one type of sustainability practice. ⢠Seven surveyed fleets (70% of the responders) plan to continue with their current sustainabil- ity practices; three fleets (30%) may consider other AF technologies/vehicles in the future if AFVs improve. Two operators do not plan to implement any sustainable practices in the near future, either because they are happy with what they have or cannot afford it. ⢠Four surveyed private GT providers face clean vehicle policies imposed by the airports. Five types of clean vehicle requirements imposed by the airports on private operators are 1. Use vehicles with fuel economy of 41 mpg or higher (typically applies to taxis). 2. Operators must implement deadhead reduction strategies (typically applies to TNCs). 3. All trips by vehicles with non-AFV comparable emissions are subject to triple airport trip fees. 4. Operators must use AFVs or AFV-comparable emissions vehicles at the airport. 5. Twenty-five percent of taxi fares from the airport should be made by clean air vehicles. ⢠Two of the surveyed operators subject to clean vehicle policies were not involved by the air- ports in policy development. Surveyed fleets indicated that only one airport solicited private fleetsâ input for developing clean vehicle requirements. ⢠Six surveyed GT fleets experienced difficulties in meeting the requirements of the airport clean vehicle policies, and two operators found compliance with the airport policy to be diffi- cult. Only three surveyed fleets were able to meet the requirements of the airport clean vehicle policies with no difficulties. ⢠Main barriers/challenges encountered by GT providers while implementing different kinds of sustainability projects include higher up-front costs (five surveyed GT fleets, 45.5% of responders), range and fueling time of AFVs (four fleets, 36.4%), access to alternative fueling infrastructure (three fleets, 27.3%), the low price of gas (two fleets, 18.2%), and lack of qualified/certified AFV mechanics (two fleets, 18.2%). ⢠Incentives currently available to private GT fleets for implementing sustainability projects include government tax credits to purchase AFVs (five surveyed fleets, 41.7% of the responders), grants/rebates to purchase/convert AFVs (three fleets, 25.0%), and lower airport trip fees for AFVs (one airport). Two surveyed fleets are not aware of any incentives; three surveyed opera- tors have no access to incentives (incentives are not available or the operators are not eligible). ⢠Surveyed fleets find government tax credits and rebates (four surveyed fleets, 36.4% of the responders) and preferential treatment of AFVs by the airports (four fleets, 36.4%) the most effective types of incentives for encouraging GT operators to adopt AFVs. Other helpful incen- tives are direct grants to purchase AFVs (three fleets, 27.3%) and longer airport agreements to operators running AFVs (three surveyed GT fleets, 27.3%).
Results 49 ⢠Fleet recommendations for designing effective airport clean vehicle policies include: 1. Ensuring fleet access to fuel by providing fueling infrastructure at the airport (six surveyed GT fleets, 50% of the responders). 2. Involving GT providers while developing clean vehicle policies (three fleets, 25%). 3. Treating all operators equally/fairly (three fleets, 25%). 4. Offering longer and/or exclusive contracts with operators that implement AFVs to allow adequate time for them to recoup the investment (two fleets, 16.7%). 5. Modeling clean vehicle policy after the existing airport program to ensure clarity and structure (one surveyed fleet). 6. Focusing on increasing the pool of AFVs rather than restricting the types of vehicles at the airport (one surveyed fleet) and other suggestions. ⢠Most of the surveyed GT operators were directly or indirectly affected by TNC operations at the airports. Five surveyed operators (83.3% of the responders) reported losing market share to TNCs. ⢠Common suggestions by the surveyed GT operators regarding TNCs include: 1. Airports should treat all operators equally. 2. Airport policies regarding TNCs are not helping traditional operators. TNCs face little regulation and enjoy an advantageous position compared with traditional operators. 3. Airports should not impose any more requirements on the taxicab industry, which is already struggling because of competition from TNCs. Considerations and Outstanding Issues The analysis presented in the current report is based mainly on the information obtained from the interviews of airports and airport GT fleets. The collected information reflects the opinions of the airports and fleets about AFV technologies, government incentives, and airport sustain- ability practices. No attempt was made to independently verify the accuracy of the provided information. Therefore, the results of the analysis should be interpreted accordingly. The analysis in this study is based on 24 data points (11 surveyed airports and 13 surveyed fleets). Because of the low number of observations, the conclusions of the study have no statis- tical significance and are anecdotal in nature. Therefore, the results of the analysis should be interpreted with caution. Although an attempt was made to select airports of different sizes for the analysis, most of the surveyed airports are large hubs. Medium-size airports and especially small airports are under- represented in the data sample. Smaller airports may have a different perspective on the clean vehicle policies and strategies or other sustainability practices. Therefore, a more balanced mix of airports of different sizes may improve the reliability of the analysis. Additionally, it may be useful to examine in more detail how airport size affects the choice of various types of clean vehicle policies implemented by the airport. Not all surveyed airports track the impact of their sustainability practices due to a lack of resources or available tracking mechanisms. Some airports that do regularly track the overall environmental impact of the airport are unable to separate the total impact by various contribut- ing sources. As a result, the success of clean vehicle policies is often evaluated anecdotally rather than by objective measurements. Performing a more in-depth evaluation of the environmental impact of the airportâs clean vehicle policies will be useful for identifying successful models for encouraging higher usage of clean vehicles by the private fleets serving the nationâs airports. The advent of TNCs changed the entire landscape of the GT industry. TNCs provide on- demand transportation service on short notice using a mobile app. The TNC business model
50 Clean Vehicles, Fuels, and Practices for Airport Private Ground Transportation Providers relies on a network of personal, rather than commercial vehicles that are operated and owned by individual drivers. This allows TNCs to maintain large fleets of vehicles with no employees/ drivers and avoid the responsibility of the costs associated with owning and operating vehicles, as well as government regulations that apply to commercial vehicles. TNCs are increasingly becoming common transportation providers at airports. More and more airports sign formal agreements with TNCs for providing services to airport customers. For many airports, the experience of working with TNC operators is relatively new. Currently sufficient data do not exist to evaluate the impact of TNCs on emissions and sustainability practices at airports. The results and conclusions of the current analysis related to TNCs lack historic data and should be interpreted with caution. A more in-depth analysis of the impact of TNCs on the airportsâ environmental footprint and sustainability practices may be warranted in the near future.
