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23
Transportation Energy Management

The transportation sector accounts for 28 percent of the fossil fuel and 63 percent of the petroleum consumed in the United States, resulting in the emission of a number of greenhouse gases, including 30 percent of U.S. CO2 emissions (International Energy Agency, 1984; European Economic Community, 1988; Lyman, 1990). Petroleum-fueled personal passenger vehicles (both automobiles and light trucks) account for 58 percent of all transportation energy use (Ross, 1989) and thus the majority of transportation-related CO2 emissions.

In reviewing methods of reducing greenhouse gas emissions from the transportation sector, the panel focused on three areas: vehicle efficiency, alternative transportation fuels, and transportation system management.

In the short run, transportation energy consumption can change rapidly as consumers adjust their demands concerning when and how to travel. On a slightly longer time scale, higher vehicle and fuel prices, along with shifts in vehicle and transportation demand, will lead to changes in the types of vehicles in use. On a significantly longer time scale, investments can be made in alternative transportation fuels, construction of new mass transit facilities and high-occupancy-vehicle (HOV) lanes, land use planning and jobs/housing balance, research and development, and tooling for technological improvements.

Vehicle Efficiency

The oil embargoes of the 1970s heightened concern for the efficient use of energy in the transportation sector. In the 1980s, however, declining oil costs led to reduced vehicle operating costs, and the concern for energy efficiency diminished. More recently, oil prices have begun to rise again,



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Page 286 23 Transportation Energy Management The transportation sector accounts for 28 percent of the fossil fuel and 63 percent of the petroleum consumed in the United States, resulting in the emission of a number of greenhouse gases, including 30 percent of U.S. CO2 emissions (International Energy Agency, 1984; European Economic Community, 1988; Lyman, 1990). Petroleum-fueled personal passenger vehicles (both automobiles and light trucks) account for 58 percent of all transportation energy use (Ross, 1989) and thus the majority of transportation-related CO2 emissions. In reviewing methods of reducing greenhouse gas emissions from the transportation sector, the panel focused on three areas: vehicle efficiency, alternative transportation fuels, and transportation system management. In the short run, transportation energy consumption can change rapidly as consumers adjust their demands concerning when and how to travel. On a slightly longer time scale, higher vehicle and fuel prices, along with shifts in vehicle and transportation demand, will lead to changes in the types of vehicles in use. On a significantly longer time scale, investments can be made in alternative transportation fuels, construction of new mass transit facilities and high-occupancy-vehicle (HOV) lanes, land use planning and jobs/housing balance, research and development, and tooling for technological improvements. Vehicle Efficiency The oil embargoes of the 1970s heightened concern for the efficient use of energy in the transportation sector. In the 1980s, however, declining oil costs led to reduced vehicle operating costs, and the concern for energy efficiency diminished. More recently, oil prices have begun to rise again,

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Page 287 and that, combined with a growing concern about greenhouse warming and the role of CO2 as a greenhouse gas, has once again focused attention on the efficient use of transportation fuel. Vehicle efficiency involves technological improvements in fuel economy—improving the miles per gallon of vehicles. The more efficient a vehicle is, the less fuel it burns to travel a given distance. The less fuel it burns, the lower are the amounts of CO2 emitted. These methods of emission reduction and their cost-effectiveness are evaluated in the following sections for light-duty vehicles, heavy-duty trucks, and domestic air carriers. The emphasis is on light-duty vehicles because they represent the largest and most thoroughly studied sector. Table 23.1 shows the amount of fuel used by each type of vehicle for different modes of operation. The information presented here indicates that light-duty vehicles consume the largest quantity of transportation fuel, with heavy-duty trucks second and aircraft third. Recent Trends The recent trend in fuel economy from 1975 to 1989 for the new U.S. passenger car fleet is presented in Figure 23.1a (Amann, 1989). Figure 23.1b shows the fuel economy index (FEI) for the period from 1930 to 1990. The FEI is an index of powertrain efficiency including weight and performance. Studies by Leone and Parkinson (1990) and by Greene (1989) indicate that the trend in the period from 1975 to 1982 was a response to increased fuel prices and fuel economy regulations. As discussed below in the ''Barriers to Implementation" section, there is some disagreement on the relative impact of fuel prices and regulations on the supply of fuel-efficient vehicles. The vehicles manufactured during that period were, on the average, 450 kg (1000 pounds) lighter within each market segment, were degraded in performance and other attributes, and incorporated various fuel-efficient technologies. Figure 23.2 indicates how consumer preferences for vehicles changed from 1972 to 1986. As shown, some consumers accepted the smaller vehicles offered to improve energy efficiency, while others resisted the change in performance and either did not buy cars or shifted to light-duty trucks and vans. Because market conditions and fuel prices cause consumer preferences for fuel-efficient vehicles to change over time, one should distinguish between the trends in overall vehicle fuel economy and powertrain efficiency. Therefore it is important to look not only at miles per gallon but also at the FEI. The FEI is used to control for other vehicle changes, as shown in Figure 23.1b for the period from 1930 to 1990. This parameter, used to judge passenger cars for many decades, provides a better indicator of powertrain efficiency than does fuel economy alone by controlling for both weight and performance.

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Page 288 TABLE 23.1 Transportation Energy Use by Mode, 1987         Energy Use (trillion Btu) Thousand Barrels per Day Crude Oil Equivalenta Percentage of Total Highwayb 16,213.5 7,658.1 73.6 Automobiles 8,862.9 4,186.2 40.3 Motorcycles 24.6 11.6 0.1 Buses 156.8 74.1 0.7   Transit 74.3 35.1 0.3   Intercity 21.6 10.2 —c   School 60.9 28.8 0.3 Trucks 7,169.2 3,386.2 32.6   Light trucksd 4,031.9 1,904.4 18.3   Other trucks 3,137.3 1,481.8 14.2 Off-Highwayb (heavy duty)e 665.2 314.2 3.0 Construction 209.9 99.1 1.0 Farming 455.3 215.1 2.1 Nonhighwayb 4,490.6 2,121.0 20.4 Air 1,893.9 894.5 8.6   General aviationf 139.1 65.7 0.6   Domestic air carriers 1,564.2 738.8 7.1   International air carriers 190.6g 90.0 0.9 Water 1,326.0 626.3 6.0   Freight 1,095.7 517.5 5.0     Domestic trade 370.7 175.1 1.7     Foreign trade 725.0 342.4 3.3     Recreational boats 230.3 108.8 1.0 Pipeline 775.0 366.1 3.5   Natural gas 562.9 265.9 2.6   Crude petroleum 91.0 43.0 0.4   Petroleum product 67.4 31.8 0.3   Coal slurry 3.7 1.7 —c   Water 50.0 23.6 0.2 (continued on page 289)

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Page 289 (Table 23.1 continued from page 288)         Energy Use (trillion Btu) Thousand Barrels per Day Crude Oil Equivalenta Percentage of Total Rail 495.7 234.1 2.2   Freighth 471.9 197.4 1.9     Transit 41.0 19.4 0.2     Commuter rail 21.4 10.1 —c       Intercity 15.4 7.3 —c Military Operations 647.3 305.7 2.9   TOTALi 22,016.6 10,399.0 100.0 aBased on Btu content of a barrel of crude oil. bCivilian consumption only; military consumption shown separately. cNegligible. dTwo-axle, four-tire trucks. e1985 data. fAll aircraft in the U.S. civil air fleet except those operated under CFR parts 121 and 127 (i.e., air carriers larger than 30 seats or a payload capacity of more than 7500 pounds). General aviation includes air taxies, commuter air carriers, and air travel clubs. gThis figure represents an estimate of the energy purchase in the United States for international air carrier consumption. hIncludes Class 1, 2, and 3 railroads. iTotals may not include all possible uses of fuels for transportation (e.g., snowmobiles). SOURCE: Davis et al. (1989). An envelope of currently "acceptable trades" in the United States is shown in Figure 23.3 in a schematic calculated by Amann (1989). The envelope represents measured performance and fuel economy data for 50 different models of cars produced in 1985 and 1986, all equipped with automatic transmissions. The y-axis in Figure 23.3 represents FEI, the product of vehicle mass and fuel economy. The weight class averages are from 1979, 1984, and 1989. The weight is defined as the test-weight class and the fuel economy is measured by the Federal Test Procedure, both as defined by the Environmental Protection Agency (EPA). The performance index on the x-axis is the time (in seconds) required to accelerate from 0 to 60 mph. Though subject to abuse, performance is an attribute desired for freeway merging, highway passing, hill climbing, and towing. The negative slope of this parallelogram quantifies the inherent trade-off between fuel economy and performance for a car of given mass and level of powertrain technology. Emission Control Methods The efficiency of transportation vehicles can be increased in a number of ways, including improving the engine and transmission efficiency, reducing

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Page 290 image FIGURE 23.1 Fuel economy trends. The fuel economy index (FEI) is an index of powertrain efficiency, the product of vehicle mass and fuel economy. SOURCE: Data are from Amann (1989).

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Page 291 image FIGURE 23.2 Components of change in light-duty vehicles. SOURCE: U.S. Department of Energy (1989). weight, improving vehicle aerodynamics, and reducing the tire-rolling resistance.Each of these methods and their cost are discussed below. Technological Improvements in Light-Duty and Heavy-Duty Vehicles Efforts to improve conventional gasoline engines focus on obtaining the optimal engine operation possible through methods such as improving part-load operations (power required at less than peak efficiency) and combustion characteristics, reducing engine warm-up time, increasing compression ratios, reducing frictional losses, and extending the operating regime of engines (Bleviss, 1988). Another method of improving vehicle efficiency is to increase transmission efficiency. The focus here is on reducing the losses associated with either automatic or manual transmissions through design changes. Automatic transmissions provide shifting at the optimal moment (unlike manual transmissions, which depend on the driver) so that the vehicle can remain at full load, but they have pumping and frictional losses. Manual transmissions do not have these losses. However, drivers do not generally operate manual transmissions at maximum efficiency by shifting at the optimal moment. A number of methods for increasing transmission efficiency have

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Page 292 image FIGURE 23.3 Fuel economy index (FEI) versus performance index. Envelope of fuel economy and performance measures for a 50-car population of 1985–1986 vehicles with automatic transmissions. Circles contain averages for the six EPA weight classes in 1979. Performance index is defined as the time (in seconds) required to accelerate from 0 to 60 mph. The lower the performance index, the better the performance. SOURCE: Amann (1989). been suggested, including designs that include the continuously variable transmission (CVT). Reducing a vehicle's weight can yield major improvements in fuel economy. By reducing the weight of a vehicle 10 percent, city fuel economy can be improved 7 to 8 percent, and highway fuel economy 4 to 5 percent. The weight of the vehicle is reduced by substituting advanced materials for the steel and cast iron that were used in the past. New materials that can reduce vehicle weight include high-strength low-alloy (HSLA) steel, aluminum, magnesium, and plastics (Bleviss, 1988). Improving the aerodynamics of a vehicle involves changing the exterior

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Page 293 structure through changes in areas such as wheel openings, windshield wiper location, glass location, and underbody. A 10 percent decrease in aerodynamic drag will result in a 5 to 6 percent (highway) and 2 to 3 percent (city) reduction in fuel consumption (Bleviss, 1988). Another method of improving fuel economy is to reduce tire-rolling resistance. In the 1970s the introduction of radial and P-metric tires improved average fuel economy by 5 to 9 percent relative to the previously used bias-ply tires. Currently, a 10 percent improvement in tire-rolling resistance improves vehicle fuel economy by 3 to 4 percent (Bleviss, 1988). Additional fuel economy improvements can be made by improving the efficiency of vehicle accessories such as the air conditioner, alternator, power steering, water pump and fan, oil pump, and lights (Bleviss, 1988). Approximately 20 percent of the fuel expended on the U.S. highway system is utilized by heavy trucks and other heavy-duty vehicles. The opportunities to conserve fuel and minimize emissions parallel those for light-duty vehicles and light-duty trucks. Technological Improvements in Aircraft The third most significant component of transportation energy use is that of domestic airlines. The most advanced new jet aircraft are far more efficient than older aircraft still in service. Carlsmith et al. (1990) estimate that on a 1000-mile trip, aircraft produced in the 1960s are capable of between 40 and 50 seat-mpg, while the new Boeing 757 and 767 now in service have a fuel efficiency of 70 seat-mpg. Improvements now being introduced arise from a combination of higher-bypass-ratio engines, increased compressor and turbine efficiencies, and more energy-efficient flight planning and operations. Like highway vehicles, aircraft can also benefit from weight reduction and better aerodynamics. Efficiencies approaching 130 to 150 seat-mpg are estimated for planned vehicles utilizing improved fanjets along with other new technologies. A 20 percent gain for some existing vehicles in the fleet can be achieved via improved fanjet technology alone. Cost Estimates for Vehicles and Air Carriers Costs for achieving higher fuel economy for light- and heavy-duty vehicles have been derived from data produced in three studies. Data from the Mellon Institute study (Shackson and Leach, 1980) and from two Department of Energy (DOE) studies (Ledbetter and Ross, 1989; Difiglio et al., 1990) were assembled (see Appendix E) to calculate the three different curves in Figures 23.4 (6 percent discount rate) and 23.5 (30 percent discount rate). These curves show the cost in dollars per gallon relative to the improvement in on-road fuel economy. Values from the average new car

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Page 294 image FIGURE 23.4 Cost of gasoline and efficiency (6 percent discount rate). image FIGURE 23.5 Cost of gasoline and efficiency (30 percent discount rate).

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Page 295 fleet efficiencies along with the average fuel prices for Japan, Sweden, United Kingdom, United States, and West Germany have been plotted as squares on the same figures. Cost-effectiveness values are highly uncertain and vary significantly from technology to technology. Although some cost-effective technologies create a net savings to the consumer, less efficient technologies generate costs exceeding $10/t CO2 equivalent (at 6 percent discount rate) for those not involving life-style adjustments and more than $700/t CO2 (at 6 percent discount rate) for those that involve changes in life-style.1 The costs are much higher when a discount rate of 30 percent is used—the rate of return consumers generally desire for investing in vehicle efficiency. Overall cost estimates depend on a variety of assumptions involving the costs, effectiveness, and interactions of technology combinations as well as consumer preferences and market behavior. Further complications arise from variations in the cost structures of different manufacturers, variations across market segments, cost differences due to exchange rates, and international differences in driving behavior and vehicle use patterns. The discontinuity in the slope of the Difiglio curve at approximately 31 mpg (on-road fuel economy) is the arbitrary point at which sales shifts in the vehicle mix are required to gain higher average fuel economy levels. Difiglio has labeled this point the "maximum technology" point for the year 2000.2 In the region beyond this arbitrarily defined point, downsizing of the fleet or development of expensive technology will be required to achieve future efficiency improvements. Efficiency gains beyond this point are achieved by downsizing (which reduces passenger and carrying capacity) and by compromising other attributes such as performance, comfort, and safety. The average cost-effectiveness values, as distinct from marginal cost-effectiveness values, which increase substantially as one moves past 25 mpg, are summarized in Table 23.2 as a function of discount rate for all three cost curves (see Appendix E). This table shows the net implementation cost and potential emission reduction for light-duty vehicles, heavy-duty trucks, and aircraft. Both the more accurate full-cycle emission accounting and an accounting including only the emissions generated during consumption are shown. Cost and emission reductions for light-duty vehicles are shown for the three analyses available for that sector. The net implementation cost—which subtracts the fuel saved from the implementation cost—is presented for four different interest rates (3, 6, 10, and 30 percent). Beyond the "maximum technology" point, the amount of CO2 reduction and the corresponding cost-effectiveness values are summarized in Table 23.3, which repeats the analysis in Table 23.2 for improvements that involve life-style adjustment—the "maximum technology" point on the Difiglio supply curve shown in Figures 23.4 and 23.5. The net implementation cost and potential emission reduction are shown in Table 23.3 for light-duty vehicles, both with the more accurate full-cycle emission accounting

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Page 296 TABLE 23.2 Implementation Cost of Vehicle Efficiency Improvements with No Change in Fleet Mix   Net Implementation Cost ($/t CO2 equivalent)     d = 3% d = 6% d = 10% d = 30% Emission Reduction (Mt CO2 equivalent/yr) Full-Cycle Emission Accounting           Light vehicle, Ledbetter and Ross -52 -50 -46 -2 379 Light vehicle, Shackson and Leach -10 -1 +10 +191 389 Light vehicle, Difiglio -26 -22 -13 +128 397 Heavy truck -42 -38 -32 +45 61 Aircraft retrofit     +230   13             Consumption Emission Accounting           Light vehicle, Ledbetter and Ross -81 -78 -71 -3 245 Light vehicle, Shackson and Leach -16 -2 +16 +296 251 Light vehicle, Difiglio -40 -34 -20 +198 256 Heavy truck -65 -59 -50 +70 39 Aircraft retrofit     +357   8

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Page 319 Land use planning strategies that local governments and planners can use to manage travel demand include requiring land use plans and zoning to be consistent with transportation capacity, planning future development densities to accommodate present and future transportation capacity, and restricting uses that generate excessive numbers of trips (Deakin, 1989). Another set of regulatory approaches focuses on reducing trips associated with new developments by requiring developers to meet certain site design criteria, provide for transportation and other infrastructure, and comply with trip reduction ordinances (Suhrbier and Deakin, 1988). The Southern California Association of Governments (SCAG) has proposed one of the most far-reaching land-use-oriented TDM programs—the redistribution of some population growth into job-rich areas and some jobs growth into housing-rich areas in order to promote jobs/housing balance (Southern California Association of Governments, 1989). Employer-based TDM programs have successfully changed commuting behavior and reduced the use of single-occupant vehicles. A recent survey by the Federal Highway Administration concluded that TDM programs, especially when undertaken in conjunction with parking management programs, should normally be able to achieve trip reductions in the range of 20 to 40 percent (U.S. Department of Transportation, Federal Highway Administration, 1990). TDM programs can be even more effective if they address some of the reasons commuters prefer to drive (e.g., the need to leave children at day care and concern that the car may be needed during the day for emergencies) through methods such as provision of day care at the work site and guaranteed ride home programs for emergencies (U.S. Department of Transportation, Urban Mass Transportation Administration, 1989a; U.S. Department of Transportation, Federal Highway Administration, 1990). The cost of TDM programs varies widely depending on the measures used, the size of the employer, and other factors. Costs are frequently in the range of $15 to $55 per employee, but may be as high as $100 per employee per year (Municipality of Metropolitan Seattle, Service Development Division, 1989; U.S. Department of Transportation, Urban Mass Transit Administration, 1989a). Using TDM to increase average vehicle occupancy could be a cost-effective way of reducing CO2 emissions. In the United States the average occupancy level of commuter vehicles is only 1.1 persons per vehicle. If this could be increased to 2.1 persons per vehicle, 30 to 40 million gallons of gasoline would be saved daily (American Public Transit Association, 1989). While increasing the peak-hour vehicle occupancy rate to 2.1 persons per vehicle would be a daunting (some would say impossible) task, achieving this long-term goal would result in an annual CO2 reduction of 98 to 131 Mt. Even if the TDM costs needed to achieve this goal are as high as $100 per employee per year for each of the 96.7 million workers in the United States (Pisarski, 1987), the offsetting gasoline savings of $10.95 billion per year ($1/gallon for 30 million gallons/day) would eliminate 98 Mt of CO2 emissions at a cost of -$13/t.

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Page 320 High-Occupancy-Vehicle Lanes Pricing measures, parking management, and transportation demand management are all designed at least in part to increase average vehicle occupancy during peak commuting hours. One way of accommodating the increased number of multioccupant vehicles would be to increase the supply of specially designated high-occupancy-vehicle (HOV) lanes. Such lanes are built for the exclusive use of buses, vanpools, and (sometimes) carpools carrying three or more persons. In recent years, construction of HOV lanes has gained acceptance as an effective means of reducing commuting time, encouraging ridesharing, and increasing vehicle occupancy rates (Southern California Association of Governments, 1989). HOV lanes can reduce commuting time on congested highways by 45 to 50 percent and also reduce the total VMT (Davis et al., 1989; Institute of Transportation Engineers, 1988). The Institute of Transportation Engineers has concluded that HOV lanes are often the lowest-cost type of fixed transit facility, with benefit-cost ratios in excess of 6 (Institute of Transportation Engineers, 1988, 1989). Despite these advantages, HOV lanes—especially when converted from existing general-purposes lanes—have met with political opposition from drivers upset by the sight of seemingly unused capacity in the more free-flowing HOV lanes. High-occupancy-vehicle lanes often cost far less than equal amounts of new highway capacity because each HOV lane (both at and well before the point at which the incentive to drive in the lane reaches zero) carries more persons than a regular highway lane. Costs generally range from $30,000 to $2 million per lane-mile when existing lanes are converted to HOV lanes and from $4 to $8 million per lane-mile when HOV facilities are constructed in existing or separate rights of way (Turnbull and Hanks, 1990). Other Benefits and Costs By reducing fuel use, vehicle use, and traffic congestion, transportation system management measures produce a variety of benefits in addition to CO2 emission reductions. These include reducing dependence on imported oil, lowering emissions of conventional and toxic air pollutants, and avoiding productivity losses from delays in the movement of goods and people. These benefits may total tens of billions of dollars. At the same time, there are costs—including potential consumer welfare losses from required life-style changes—incurred in adopting transportation demand measures. Reducing transportation energy use could significantly improve the U.S. balance of trade and energy security position. The transportation sector accounts for approximately two-thirds of all U.S. oil use, an amount greater than that produced domestically (Davis et al., 1989). The direct costs of

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Page 321 importing petroleum products account for nearly 40 percent of the U.S. trade deficit. The United States incurs other costs because of this dependence on imported oil, including those related to using the military to protect strategic supply regions, maintaining the Strategic Petroleum Reserve, and living with the risk of supply disruptions. These costs have been estimated at between $21 billion and $125 billion annually (Greene et al., 1988), or $7 to $40 for each of the 8.3 million barrels of oil imported daily during the first four months of 1990. Reducing VMT will reduce emissions of air pollutants, for which permissible standards are set in terms of grams of pollutant emitted per mile. The transportation sector, particularly light trucks and automobiles, is responsible for a large proportion of U.S. air pollution, particularly in urban areas. Motor vehicles emit five of the six "criteria" pollutants regulated under the Clean Air Act, including fine particulates and • 70 percent of CO; • 40 percent of volatile organic compounds, which are precursors to the formation of ozone, the primary component of urban smog; • 40 percent of NOx, regulated pollutants that are precursors to both acid rain and photochemical air pollution; and • 35 percent of lead, a potent neurotoxin particularly dangerous to young children (MacKenzie, 1988; U.S. Office of Technology Assessment, 1989). Motor vehicles are also responsible for a variety of toxic emissions (especially benzene and formaldehyde) from exhaust and gasoline vapors, all of which also could be reduced by greenhouse gas mitigation measures. Air pollution adversely affects human health and the environment. Estimates of the total societal cost of pollutant emissions from refineries, fueling stations, and motor vehicles range from $11 billion to $187 billion annually, depending on assumptions about both the numbers of deaths and illnesses and the monetary value assigned to the loss of life (Greene et al., 1988). Another benefit of transportation system management is that measures limiting the number of VMT or reducing the degree of congestion encountered while traveling avoid substantial productivity losses from delays in the movement of goods and people. National estimates of delay on urban highways and resulting productivity losses have been prepared by the Federal Highway Administration and reviewed by the General Accounting Office. In 1987, highway delays cost motorists $7.8 billion in wasted time. By 2005 the cost of delays is projected to increase to $29 billion to $43 billion. Another type of lost productivity is the cost of delaying trucks carrying goods. The Federal Highway Administration has estimated that the total annual cost of truck delay on highways alone is $4.2 billion to $7.6 billion; additional trucking productivity losses from congestion on urban

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Page 322 streets would add $19.4 billion to $22.9 billion to this total (U.S. General Accounting Office, 1989). These estimates of $52.6 billion to $73.5 billion in annual productivity losses at current congestion levels do not include delays faced by commuters on local streets or the costs of tardiness to employers. When surveyed, employers frequently cite reductions in tardiness and absenteeism as reasons for sponsoring ridesharing programs. One survey of 20 such programs found that 18 of 20 ridesharing programs had cost-benefit ratios greater than 1 when the benefits of reduced tardiness, absenteeism, and need to construct parking facilities were calculated; cost-benefit ratios were frequently in excess of 10 (Wegmann, 1989). Despite these benefits, there are costs—primarily in the form of consumer welfare losses—that will likely occur due to efforts to reduce solo commuting and vehicle usage. For many workers, commuting could take longer and result in lost productivity. A typical mass transit commute in the United States averages 13 to 14 mph, whereas commuters driving alone or in a carpool travel at 31.5 to 33.5 mph while covering a comparable distance (Pisarski, 1987). (Although such losses cannot be quantified, commuters and other drivers will also suffer "consumer welfare" losses from real or perceived reductions in personal mobility and freedom.) These consumer welfare losses can, however, be minimized by focusing transportation system management efforts on reducing commuters' travel time. Transit can be made more convenient and faster; HOV lanes can be used to reduce travel time for buses, vanpools, and carpools. Differences in commuting time between automobiles and other modes will also narrow if congestion increases automobile travel times: average vehicle speeds in southern California are projected to fall to 19 mph in the absence of transportation system management (Southern California Association of Governments, 1989). In addition, behavioral studies indicate that commuters are more concerned about travel time reliability than total elapsed travel time (Wachs, 1989); thus minimizing variations in travel time on mass transit and in the use of HOV lanes should reduce consumer welfare losses. Research and Development Needs The research and development needs for each of the three primary mitigation options described above are listed in this section. Recently, the National Research Council's (1990) alternative energy research and development study made the following recommendations: • Improve batteries for vehicle propulsion to achieve higher performance and durability and to reduce costs. • Adapt alternative fuels (e.g., alcohols) to engines and vehicles. • Reduce emissions from efficient power plants such as the diesel.

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Page 323 • Evaluate vehicle systems to ensure the safety of smaller cars built with lightweight structural materials. • Investigate innovative electric transportation systems. The Mitigation Panel would also include hydrogen in the list of alternative fuels that need to be adapted to current engines and vehicles and would note that the focus of these alternative fuel efforts should be generation of fuels (such as methanol) from sources such as biomass and nonfossil electricity that do not increase greenhouse gas emissions. Since the method by which primary energy is generated is such an important factor in alternative transportation fuels, a number of research and development recommendations in the energy supply sector (see Chapter 24) are also applicable here. Transportation system management has, to date, been a largely empirical exercise—governments and private employers put measures into effect and only subsequently evaluate which work or why. Surveys, pilot programs, and other research tools should be used to predict and evaluate which methods are most effective in altering transportation behavior. In particular, the relative efficacy of different pricing mechanisms—gasoline taxes, parking fees, tolls, sales taxes, and registration fees—should be evaluated (Deakin, 1990; Hillsman and Southworth, 1990). Conclusions The transportation sector accounts for 30 percent of CO2 emissions. Changes in transportation over the next several decades could substantially affect the nation's contributions to greenhouse warming. Moreover, such changes are likely to influence practices elsewhere as well. For these reasons, a focus on transportation is an important component of policy. Of the three different types of methods for reducing greenhouse gas emissions from the transportation sector, vehicle efficiency has the greatest potential. However, implementation of vehicle efficiency measures will be slow because of the low turnover of vehicles in the marketplace and the time delay between design and production of vehicles. Each of the alternative transportation fuels has problems. Biomass fuels require production systems and infrastructures not currently available. In addition, there is concern about the ability to convert sufficient land to grow corn for ethanol or woody biomass for methanol or ethanol. For hydrogen, the production systems and infrastructure would have to be created. There are storage and safety concerns to be resolved for vehicles having on-board reservoirs of hydrogen. If hydrogen is to be used to reduce greenhouse gas emissions, it must be made by using nonfossil-fuel-generated energy. Electric vehicles are a viable option only if the electricity is produced from nonfossil fuels. Further technological advances, particularly with batteries,

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Page 324 but probably also involving the electrical charging infrastructure, are needed to produce electric vehicles that will be as convenient to use as today's fossil-fuel-powered vehicles. If alternative fuels are to serve as a significant alternative to gasoline in the next century, the federal government will have to both increase funds for research and development programs and tax gasoline to reflect its full social costs and make alternative fuels cost-competitive. In the interim, alternative fuels should not be used if the switch from gasoline increases life-cycle carbon emissions. In the area of transportation system management, supply-side measures such as providing HOV lanes and increasing mass transit capacity—and demand-side measures involving pricing, parking availability, and transportation demand management—can cost-effectively and substantially reduce vehicle miles traveled, traffic congestion, fuel use, and CO2 emissions. One particularly attractive feature of transportation demand management is that CO2 emission reductions could occur during the period when fuel economy changes are being phased in; these measures will also protect fuel economy improvements in the longer term. To gain these benefits, barriers such as inappropriate transportation pricing and lack of alternatives must be overcome. In addition, steps must be taken to reduce potential consumer welfare losses due to increases in commuting time and reductions in personal freedom. Transportation system management has the potential, however, to be a cost-effective CO2 reduction strategy for small amounts of CO2 reduction while fulfilling its primary goal of providing mobility for people at the least total cost to society. Major uncertainties stand in the way of large-scale reductions in greenhouse gas emissions from transportation. Several are discussed here because they are especially important to U.S. national policy: • Uncertainty over the degree of willingness of vehicle owners (households and firms) to purchase smaller, more fuel-efficient vehicles when fuel prices are low poses a significant barrier to the adoption of more fuel-efficient vehicles. Ways of overcoming this barrier while preserving the dynamics of competition in the U.S. vehicle market will have to be identified, evaluated, and implemented. • Policies aimed at altering vehicle use, including fuel pricing, transportation demand management, and changes in urban design, also face large uncertainties. Promising attempts are beginning in southern California, motivated by concern over air quality. Careful monitoring and deliberate experimentation in this and other metropolitan areas could yield important findings over the next decade. Perhaps the largest uncertainty is the degree to which consumers and voters will be willing to respond to changing price and policy signals by

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Page 325 buying more fuel-efficient cars, changing commuting patterns, and otherwise altering their life-style. One should bear in mind that the emergence of current vehicle use patterns in industrialized societies occurred over the last half-century, a time span comparable with that in which greenhouse warming may occur. Notes 1. Throughout this report, tons (t) are metric; 1 Mt = 1 megaton = 1 million tons; and 1 Gt = 1 gigaton = 1 billion tons. 2. Subsequent to the preparation of these results, K. G. Duleep (co-author with Difiglio and Greene) has refined the estimate of the ''maximum technology" point. Duleep estimates that in 1996 all available technologies could produce a CAFE mpg of 29.3 (22.5 on-road) and in 2001 all available technologies could produce a CAFE mpg of 36.0 (27.7 on-road) (Plotkin, 1991). References Altshuler, A., M. Anderson, D. Jones, R. Roos, and J. Womack. 1984. The Future of the Automobile. Cambridge, Mass.: MIT Press. Amann, C. A. 1989. The automotive spark-ignition engine—An historical perspective. In History of the Internal Combustion Engine, ICE, Volume 8, Book No. 100294-1989, E. F. C. Somerscales and A. A. Zagotta, eds. New York: American Society of Mechanical Engineers. Amann, C. A. 1990. Technical options for energy conservation and controlling environmental impact in highway vehicles. Paper GMR-6942 presented at the Energy and the Environment in the 21st Century Conference, Massachusetts Institute of Technology, Cambridge, Mass., March 26–28, 1990. American Public Transit Association. 1989. Transit Fact Book. Washington, D.C.: American Public Transit Association. Atkinson, S. E., and R. Halvorsen. 1984. A new hedonic technique for estimating attribute demand: An application to the demand for automobile fuel efficiency. Review of Economics and Statistics 66(3):416–426. Atkinson, S. E., and R. Halvorsen. 1990. Valuation of risks to life: Evidence from the markets for automobiles. Review of Economics and Statistics 72(1):137–142. Bergeron, T. W., and N. D. Hinman. 1990. Fuel Ethanol Usage and Environmental Carbon Dioxide Production. Golden, Colo.: Solar Energy Research Institute. January. Bleviss, D. 1988. The New Oil Crisis and Fuel Economy Technologies. New York: Quorum Books. Bleviss, D., and P. Walzer. 1990. Energy for motor vehicles. Scientific American 263(Sept.):103–109. California Energy Commission (CEC). 1989. Comparing the Impacts of Different Transportation Fuels on the Greenhouse Effect. Sacramento: California Energy Commission. Carlsmith, R. S., W. U. Chandler, J. E. McMahon, and D. J. Santini. 1990. Energy

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Page 326 Efficiency: How Far Can We Go? Report ORNL/TM-11441. Prepared for the Office of Policy, Planning and Analysis, U.S. Department of Energy. Washington, D.C.: U.S. Department of Energy. Congressional Budget Office. 1980. Fuel Economy Standards for New Passenger Cars After 1985. Washington, D.C.: U.S. Congress. Davis, S. C., D. B. Shonka, G. J. Anderson-Batiste, and P. S. Hu. 1989. Transportation Energy Data Book: Edition 10. Report ORNL-6565 (Edition 10 of ORNL-5198). Prepared for the U.S. Department of Energy. Washington, D.C.: U.S. Department of Energy. Deakin, E. A. 1989. Land use and transportation planning in response to congestion problems: A review and critique. Pp. 77–86 in Congestion, Land Use, and Transportation Planning. Transportation Research Record No. 1237. Washington, D.C.: Transportation Research Board, National Research Council. Deakin, E. A. 1990. Suburban Traffic Congestion, Land Use and Transportation Planning Issues: Public Policy Options in Traffic Congestion and Suburban Activity Centers. Transportation Research Circular No. 359. Washington, D.C.: Transportation Research Board, National Research Council. De Luchi, M. A., R. A. Johnston, and D. Sperling. 1988. Transportation fuels and the greenhouse effect. Transportation Research Record 1175:33–44. Difiglio, C., K. G. Duleep, and D. L. Greene. 1990. Cost effectiveness of future fuel economy improvements. The Energy Journal 11(1):65–86. European Economic Community (EEC). 1988. Energy analysis of the transport sector: Determining factors and forecasts. In Energy in Europe: Energy Policies and Trends in the European Community. Brussels: Directorate General for Energy, European Economic Community. Godek, P. E. 1990. The Corporate Average Fuel Economy Standard 1978–1990. Working Paper, October. Greene, D. L. 1989. CAFE or Price?: An Analysis of the Effects of Federal Fuel Economy Regulations and Gasoline Price on New Car MPG, 1978–89. The Energy Journal 11(3):37–58. Greene, D. L., and J-T. Liu. 1988. Automotive fuel economy improvements and consumers' surplus. Transportation Research 22A:203–218. Greene, D. L., D. Sperling, and B. McNutt. 1988. Transportation energy to the year 2020. In A Look Ahead: Year 2020. Washington, D.C.: Transportation Research Board, National Research Council. Hillsman, E. L., and F. Southworth. 1990. Factors that may influence responses of the U.S. transportation sector to policies for reducing greenhouse gas emissions. Pp. 1–11 in Global Warming: Transportation and Energy Considerations 1990. Transportation Research Record No. 1267. Washington, D.C.: Transportation Research Board, National Research Council. Ho, S. P., and T. A. Renner. 1990. The global warming impact of attainment strategies using alternate fuels. Paper presented at the Air and Waste Management Association Conference on Tropospheric Ozone, Los Angeles, Calif., March 19–22, 1990. Holcomb, M. C., S. D. Floud, and S. L. Cagle. 1987. Transportation Energy Date Book: Edition 9. Report ORNL-6325. Prepared for the U.S. Department of Energy. Oak Ridge, Tenn.: Oak Ridge National Laboratory.

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Page 327 Institute of Transportation Engineers. 1988. The Effectiveness of High-Occupancy Vehicle Facilities. Washington, D.C.: Institute of Transportation Engineers. Institute of Transportation Engineers. 1989. A Toolbox for Alleviating Traffic Congestion. Washington, D.C.: Institute of Transportation Engineers. International Energy Agency (IEA). 1984. Fuel Efficiency of Passenger Cars. Paris: International Energy Agency, Organization for Economic Cooperation and Development. Ketcham, B., and S. Pinkwas. 1980. Beyond autocracy: The public's role in regulating the auto. In Technology, Government and the Future of the Automobile, D. Ginsburg and W. Abernathy, eds. Cambridge, Mass.: Harvard Graduate School of Business Administration. Kleit, A. N. 1988. The impact of automobile fuel economy standards. Working Paper 160. February 1988. Bureau of Economics, Federal Trade Commission, Washington, D.C. Kleit, A. N. 1990. The effect of annual changes in fuel economy standards. Journal of Regulatory Economics 2(2):151–172. Kwoka, J. E., Jr. 1983. The limits of market-oriented regulatory techniques: The case of automotive fuel economy. Quarterly Journal of Economics 97:695–704. Ledbetter, M., and M. Ross. 1989. Supply curves of conserved energy for automobiles. Draft paper prepared for Lawrence Berkeley Laboratory by the American Council for an Energy-Efficient Economy, Washington, D.C. Leone, R. A., and T. W. Parkinson. 1990. Conserving energy: Is there a better way? May 1990. Paper prepared for the Association of International Automobile Manufacturers, Arlington, Va. Lyman, F. 1990. The Greenhouse Trap. Boston: Beacon Press. MacKenzie, J. J. 1988. Breathing Easier: Taking Action on Climate Change and Energy Insecurity. Washington, D.C.: World Resources Institute. Marland, G., and A. Turnhollow. 1990. CO2 Emissions from production and combustion of fuel ethanol from corn. Report ORNL/TM-11180. Oak Ridge, Tenn.: Oak Ridge National Laboratory. Motor Vehicle Manufacturers Association. 1989. MVMA Motor Vehicle Facts and Figures '89. Detroit, Mich.: Motor Vehicle Manufacturers Association. Municipality of Metropolitan Seattle, Service Development Division. 1989. Transportation Demand Management Strategy Cost Estimates. Seattle: Service Development Division, Municipality of Metropolitan Seattle. National Research Council. 1990. Confronting Climate Change: Strategies for Energy Research and Development. Washington, D.C.: National Academy Press. Pisarski, A. 1987. Commuting in America: A National Report on Commuting Patterns and Trends. Westport, Conn.: Eno Foundation for Transportation, Inc. Plotkin, S. E. 1991. Testimony before Senate Committee on Energy and Natural Resources. Washington, D.C.: Office of Technology Assessment. March 20, 1991. Pucher, J. 1988. Urban travel behavior as the outcome of public policy: The example of modal split in Western Europe and North America. The Journal of American Planners Association 54(4):509–520. Renner, M. 1988. Rethinking the Role of the Automobile. Washington, D.C.: Worldwatch Institute, 1988.

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Page 329 Wachs, M. 1989. Transportation demand management: Policy implications of recent behavioral research. Paper presented at the Symposium on Transportation Demand Management, Los Angeles, October 12–13, 1989. Wegmann, F. 1989. Cost-effectiveness of private employer ridesharing programs: An employer's assessment. Transportation Research Record 1212:88–100. Willson, R., D. Shoup, and M. Wachs. 1989. Parking Subsidies and Commuter Mode Choice: Assessing the Evidence. Los Angeles: Southern California Association of Governments.