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161 This appendix is intended to provide transportation engineers and planners a better under- standing of transit operations, describe how transit-supportive roadway strategies can help provide better transit operations, and explain why improving operations is an important goal of transit agencies. The first section contrasts the service-oriented nature of transit operations to the facility- oriented nature of roadways and discusses how operating costs have much greater importance for transit service than for roadways. The second section presents a few basic bus route schedul- ing concepts that illustrate the direct relationship between bus travel speeds on a route and the routeâs operating costs. The third section discusses transit performance considerations related to transit-supportive roadway strategies. The final section highlights transit-specific references that may be consulted when planning and designing transit-supportive roadway strategies. B.1 Transit as a Service A key difference between roadway and transit agencies is that roadway agencies primarily provide facilities that roadway users can travel on at their convenience, while transit agencies pri- marily provide a service that is only available at designated times and places. If a roadway agencyâs maintenance budget is cut by half for a year, existing roadways (the agencyâs capital investments) may still be as usable as they were the previous year, although they will slowly degrade in quality and be more expensive to repair the following year. If a transit systemâs operations budget is cut by half for a year, the systemâs buses (the systemâs capital investments) will still be around, but funding will only be available to operate half of them, resulting in an immediate need to cut ser- vice, with a correspondingly severe decrease in the quality of service experienced by passengers. Because transit is a service, the cost of providing that service is a key concern of transit agencies. The largest component of a transit agencyâs operating cost is the labor required to drive the buses, although other costs such as consumable items required by buses (e.g., fuel, oil, tires) and labor costs shared by multiple buses (e.g., bus maintenance staff, schedulers, planners, customer ser- vice staff) also contribute. As a result, the hourly cost of keeping a bus in service is an important performance metric for transit agencies; in 2012, the average cost of operating one bus for 14 hours a day, 5 days a week, for an entire year was approximately $450,000, based on National Transit Database data. Given that the cost required to operate a bus over its useful life (typically around 12 years) is an order of magnitude higher than the capital cost of the bus itself, transit agencies are very interested in using buses as efficiently as possible while they are in service. The faster that a bus can travel, the fewer buses are needed to provide service at a certain headway on a route of a certain length, as is shown in the next section. A P P E N D I X B Understanding Transit Operations (for Transportation Engineers and Planners)
162 A Guidebook on Transit-Supportive Roadway Strategies B.2 Basic Route Scheduling Concepts Cycle Time Concepts Assume for the sake of example that a transit agency operates a route that is 6 miles long and that generates sufficient ridership to require service every 10 min (i.e., a bus headway of 10 min, corresponding to a frequency of 6 buses departing a stop per hour). If the average speed that a bus operates along the route during peak periods is 8 mph, including stops to serve passengers, delays at traffic signals, and other delays due to traffic interference, how many buses are required to operate on this route? The answer to this question requires determining the cycle time, the time for a bus to make a round trip on the route (running time), the time for an adequate break (layover) for the driver, and any additional time necessary to ensure that the bus can begin its next trip on time (schedule recovery time). These components are determined as follows: â¢ Running time. On a 6-mile route, a bus traveling 8 mph requires 0.75 h (45 min) to travel the route from one end to the other. Therefore, the round-trip running time is twice this amount, or 90 min. â¢ Layover time. The required minimum layover time will be specified in the driversâ contract, but a typical rule of thumb is 10% of the running time (Boyle et al. 2009), which in this case is 9 min. The layover could be scheduled to occur all at once at the end of the round trip or could be scheduled to be split between the ends of the route, which will be assumed for this example. â¢ Schedule recovery time. If travel times on the route are highly variable, the layover time may not be sufficient to ensure that a bus can depart on time for its next trip. In that case, additional schedule recovery time may be required. For the time being, it will be assumed that travel times are regular enough that no schedule recovery time is required. The sum of these three components, 99 min, cannot be divided evenly by the desired headway, 10 min, and therefore the cycle time is rounded up to the next highest value that can be divided evenly, which in this case is 100 min. The required number of buses to operate the route is the cycle time divided by the headway, or 10 buses. Figure B-1 shows how these buses are distributed along the length of the route. Although the spatial distance between buses may vary between buses along the route (depending on how fast buses can travel in each segment of the route), the time headway stays constant at 10 min if good schedule reliability can be maintained. Impact of Changes in Bus Speeds on Short-Headway Routes What would happen if the average bus speed could be increased from 8 mph to 9 mph? In this case, the round-trip running time would drop from 90 min to 80 min, the minimum layover 10 min 10 min 10 min 10 min 5 min Finishing 5 min layover Starng trip Approaching end of round trip 6 miles Figure B-1. Example distribution of buses on a route with 10-min headways.
Understanding Transit Operations (for Transportation Engineers and Planners) 163 time would become 8 min, and the cycle time would become 90 min. In this case, only nine buses would be needed to operate the route at 10-min headways. The bus that is saved could be used to improve service on another route (attracting more ridership and fare revenue for the same operating cost) or could be taken out of service (reducing overall operating costs by one peak-period bus). On the other hand, what if traffic congestion caused average bus speeds to drop from 8 mph to 7Â½ mph? The round-trip running time would increase from 90 min to 96 min, the minimum layover time would be 10 min, and the cycle time would need to be 110 min to accommodate 10-min headways, requiring 11 buses in all. Now, the transit agency would need to add a bus to the route, which (1) might require purchasing an additional bus and (2) would definitely add one busâs worth of operating costs each year. If the transit agencyâs budget does not permit adding a bus, service would need to be cut back to 12-min headways. Although this may not seem like much, each bus would need to serve 20% more passengers per trip. This means that if all the seats were taken on average at the busiest point on the route, now the aisle would be filled with passengers on average, and some trips would need to bypass stops with waiting passengers because there would be no room for them (because passengers do not arrive at an even rate over the course of an hour). Service quality would drop and some passengers would be driven away, reducing transit agency revenue. A similar scenario involving adding buses or cutting service would occur if average bus speeds stayed the same but travel times became more variable, requiring inserting some schedule recovery time into the cycle time in addition to the existing layover time to ensure that buses could depart the ends of the route on time and that schedule reliability did not suffer. Impact of Changes in Bus Speeds on Longer-Headway Routes Transit on most routes is not operated as frequently as given in the previous examples. When a route is scheduled efficiently, the required round-trip time savings may need to be close to the value of the route headway to be able to save a bus. For example, if the route operates every 15 min, the required time savings may need to be 15 min or a little less (depending on how much round- ing up is needed to produce a workable cycle time) to be able to save a bus. In many cases, it may not be feasible to save enough time using a package of transit-supportive roadway strategies to remove a bus from a route. However, this does not mean that saving time is useless. Instead, the time savings provide a buffer to counteract the effects of increasing traffic congestion that would otherwise reduce average bus speeds and require the transit agency to add a bus to a route. This, in turn, pushes the need for adding buses into the future, thereby postponing the need to purchase additional buses and postponing the need for increased operating costs. The time savings may also be noticeable to customers, resulting in improved ridership. An evaluation of TriMetâs streamlining program (Koonce et al. 2006), which involved con- solidating stops, installing curb extensions, providing transit signal priority, and using the most technologically advanced buses in the fleet on selected routes, found that insufficient time was saved to save a peak-period bus on any of the 12 routes. However, the time that was saved post- poned the need to add buses to these routes by approximately 8 years, equivalent to $13.4 million in saved operating costs over that time, plus avoiding the need for capital expenditures for new buses for those routes during that time. In addition, new ridership was generated that resulted in $1.7 million in additional fare revenue, and the streamlined routesâ on-time performance declined at half the rate of similar non-streamlined routes. All of these provide meaningful benefits for the transit agency and its passengers.
164 A Guidebook on Transit-Supportive Roadway Strategies B.3 Transit Performance Agency Stakeholders There are a variety of stakeholders with vested interests in transit operations and performance. The community at large is interested in, among other things, transitâs role in providing trans- portation choices to members of the community, the transit agencyâs role as a creator and sup- porter of jobs, transitâs role in reducing the environmental impact of the overall transportation network, and how service is distributed throughout the transit service area. Roadway agenciesâ interests include the impact of transit vehicles on roadway operations and the damage they could cause to pavement, particularly at bus stops. Passengers are interested in having service pro- vided frequently, reliably, comfortably, and conveniently close to their origins and destinations (Kittelson & Associates et al. 2013). These perspectives can be seen as competing unless one steps back and realizes that the broader view of transportation is that of the user. Users are less interested in agency and jurisdictional boundaries and more focused on completing a trip that often crosses agency and jurisdictional boundaries and may shift modes one or more times over the course of the trip. It is therefore desirable to establish multi-agency operations working groups to exchange information and to work together on common problems in order to achieve mutually beneficial operational strategies. Customer Service and Ridership Transit agencies are typically focused on providing the best quality of service feasible to ensure good customer service that maintains and builds ridership. Meeting ridership targets is essential for revenue purposes since transit agencies are typically reliant on passenger fares for a portion of their funding, and some grant funding is also linked to ridership. Key elements of transit service quality include: â¢ Safe, secure, and convenient access to transit stops (spatial access); â¢ Service frequency and days and hours of service (temporal access); â¢ Service reliability (e.g., on-time performance, ability to make transfer connections); â¢ Travel time and speed; â¢ Comfort (e.g., ability to get a seat); and â¢ Cost (e.g., fare) (Kittelson & Associates et al. 2013). All of these factors influence ridership to some extent, although more research is needed. Related to factors influenced by transit-supportive roadway strategies, ridership tends to improve by 0.3% to 0.5% for every 1% reduction in travel time (Kittelson & Associates et al. 2007), while improvements in travel time variability documented in the literature have had little or no impact on ridership (Kittelson & Associates et al. 2013), although some positive impact might be expected. Performance Metrics The following are some key performance metrics used by transit agencies that can be affected by transit-supportive roadway strategies. Ridership Ridership is typically measured as the number of transit vehicle boardings; thus, a person using two transit vehicles over the course of a one-way trip is counted as two boardings. Rider- ship is a key metric for transit agencies since it directly affects agency revenue and is a primary
Understanding Transit Operations (for Transportation Engineers and Planners) 165 indicator of how well the transit agency is performing one of its core functions: meeting the mobility needs of the residents and employees located within its service area. Ridership is also a key determinant of service levels on a transit route; if ridership drops below a transit agencyâs standard, service may eventually need to be cut, while if ridership grows sufficiently that quality of service is affected (e.g., crowded vehicles, slower travel times due to serving more passengers), service may need to be added. Cost-Related Metrics As a provider of service, transit agencies are interested in the cost of providing that service, and many of the most commonly used transit performance metrics involve operating costs (e.g., operating cost per revenue hour, revenue mile, and boarding). Cost per hour is minimally affected by transit-supportive roadway strategies, cost per mile is affected to the extent that strategies reduce the number of stops made and thus improve fuel economy and reduce vehicle wear and tear, and cost per boarding is affected when improvements to a routeâs speed attract new ridership. Reliability Because most transit service is provided according to a timetable, passengers have an expectation that they will arrive at their destination at a particular time. Passengers perceive unexpected waiting time as being 2 to 5 times more onerous than unexpected in-vehicle travel time (Kittelson & Associates et al. 2013). A common performance metric representing the passenger point of view is on-time performance (e.g., percent of trips arriving within a specified number of minutes of the scheduled time). Some transit agencies use travel time percentiles in determining how much schedule recovery time to include in the schedule (Boyle et al. 2009). Travel Time The time required to travel a route is critical in determining the number of buses required to operate the route, as was discussed earlier. In addition, the faster a bus can travel a route, the longer the distance that can be traveled in a given amount of time, which has implications for how much area can be served by a route in a given time. B.4 Reference Documents and Analysis Tools The transit industry does not rely on standard national reference documents to the degree that the traffic engineering profession does. When evaluating transit-supportive roadway strategies, practitioners often use the documents and tools discussed in Appendix A. Nevertheless, there are a few additional types of transit-focused documents that are worth highlighting. Transit Capacity and Quality of Service Manual The TCQSM (Kittelson & Associates et al. 2013) is the transit counterpart to the Highway Capacity Manual (Transportation Research Board 2010). It provides a complete set of meth- ods for evaluating the capacity of transit services and facilities and presents a framework for evaluating transit quality of service from a passenger point of view. The toolbox chapters of this guidebook identify when the TCQSM may be applicable for evaluating the potential benefits of particular strategies; in particular, it can be used to estimate the following: â¢ Average bus speeds on different types of bus lanes, â¢ Delays associated with waiting for a gap to re-enter traffic from a bus stop,
166 A Guidebook on Transit-Supportive Roadway Strategies â¢ Required bus stop length to serve a given number of buses at a specified level of reliability, and â¢ Impacts of changes in bus speeds on the quality of service perceived by passengers. The TCQSMâs speed-estimation methods can be characterized as âplanning levelâ or suitable for developing a small set of alternatives to evaluate further. Normally, a more detailed operations analysis would then be undertaken using HCM methods, microsimulation, or both, to more accurately and precisely estimate the impacts of the strategy on all roadway users. AASHTO Transit Design Guide AASHTOâs Guide for Geometric Design of Transit Facilities on Highways and Streets (2014) is intended to provide âa single, comprehensive reference of current practice in the geometric design of transit facilities on streets and highways.â This guidebookâs toolbox chapters identify when the AASHTO Transit Guide provides recommendations related to transit-supportive roadway strategies (which is relatively often). APTA Best Practices The American Public Transportation Association has begun to develop recommended practices on selected transit topics. One such practice that relates to transit-supportive roadway strategies is Designing Bus Rapid Transit Running Ways (APTA 2010), which addresses the geometric design of BRT running way alternatives, including busways on exclusive rights-of-way, exclusive bus lanes, and mixed traffic on arterials. TCRP Publications Unlike in the traffic engineering profession, most of the transit industryâs knowledge of best practices has not been summarized in a small number of key documents. Instead, TCRP publications (http://www.trb.org/Publications/PubsTCRPPublications.aspx) include guidebooks, such as this one, that present best practices on focused topics of interest to the transit industry. Transit Agency Design Manuals Larger transit agencies frequently develop design manuals or guidelines that describe their preferences for designing transit facilities. Some also describe the conditions when typically undesired roadway features (e.g., bus pullouts, speed humps) might be considered or when transit-supportive roadway strategies might be considered. Bus dimensions specific to the transit agencyâs current bus fleet are a key feature of these manuals for transportation engineers to be aware of. These are used when designing roadways and off-street facilities to accommodate buses. Buses are becoming less standardized, and standard bus templates, such as those provided in the Green Book (AASHTO 2011), may not be suitable for a particular transit agencyâs fleet.