Federal spokesman of the Environmental Protection Agency sDells out those controversial details and plans needed in 66 of this nation's air quality control regions where 60% of the population resides in order to explain. . .
I ranspwrxaxiwn
controls are really needed in the air cleanup fight Joel L. Horowitz U.S. E n v i r o n m e n t a l Protection Agency, Washington, D.C. 20460
4ir Act Amendments of 1970 directed the -~ Environmental Protection Agency ( t P A ) to establish national ambient air quality standards whose attainment would protect the public health and welfare from the adverse effects of major air pollutants. The pollutants for which health-based air quality standards now exist include carbon monoxide and photochemical oxidants, presence of which in urban air is primarily attributable to automobile emissions of carbon monoxide (CO), hydrocarbons (HC). and nitrogen oxides (NO,). The air quality standard for CO is exceeded in 42 air quality control regions (AOCR's) in the U.S., and the oxidant standard is exceeded in 56 (Table 1 ) . The 66 AQCR's where at least one of these standards is exceeded contain approximately 60% of the nation's population. The automobile is the source of roughly 70-90% of CO emissions, 50-80% of HC emissions, and 40-50% of NO, emissions, depending on the AQCR. Because of the importance of the automobile relative to other sources of CO, HC. and NO, the reduction of automobiie emissions is a major objective of programs to improve air quality. The principal means of achieving this objective is the control of emissions from new cars. Since 1968 nationally and 1966 in California, new cars have been subject to increasingly stringent emissions standards. As a result, new model year 1974 cars emit only about 25% as much CO and HC and 65% as much NO, as pre1968 cars. Present law requires model year 1976 cars to emit less than 5% of the CO and HC emitted by pre-1968 cars. In addition, model year 1977 cars must have their NO, levels reduced to about 10% of pre-1968 levels. The new car controls are expected to produce substantial reductions in automobile emissions as old, highemitting cars are replaced by newer and cleaner vehicles (Figure 1). By 1985, when most cars in use will be equipped with 1976-77 emissions controls, the automobile population as a whole will emit approximately 20% of the HC, CO, and NO, that it now emits. Despite these emissions reductions, the new car controls, even when accompanied by maximum feasible control of nonautomotive emissions, do not reduce automobile emissions enough to achieve and maintain the air quality standards for CO and oxidant in all AQCR's. The three principal reasons for this are: 0 The new.car controls reduce emissions gradually as new cars replace old ones. This replacement does not necessarily happen fast enough to satisfy the Clean Air Act's requirements that the air quality standards be achieved by 1977. 0 Some regions are so severely polluted that control only of new cars and nonautomotive emissions sources will not result in the achievement of the air quality standards any time in the foreseeable future. After 1985, automobile emissions are likely to increase gradually due to growth in automobile use. There are now 30 AQCR's in which the new car controls must be supplemented by additional measures to reduce automobile emissions (Table 1). The additional measures, called transportation controls. can be divided into two general classes: measures that reduce in-use automobiles' emissions rates (i.e., emissions per mile ~
traveled), and measures that reduce automobile travel. The former class includes inspection/ maintenance and retrofit. The latter includes transit improvements. carpooling programs, and restrictions on the use of automobiles. Inspection/maintenance ( I M ) I M consists of an exhaust emissions test (inspection) followed by appropriate maintenance i f emissions are found to be excessive. The inspection phase requires the availability of a suitable short emissions test procedure. The accepted standard technique for estimating road emissions. the Federal Certification Test Procedure, is too costly and time consuming to be feasible for inspecting large numbers of vehicles. Two types of short emissions tests are now available. In the idle emissions test the exhaust gas is analyzed for CO and HC using a tail pipe concentration measurement during idle operating conditions. Vehicles with excessive emissions are required to undergo maintenance. Ordinarily, excessive HC emissions are related to the secondary ignition system, idle adjustments, and valve malfunctions. High CO emissions are indicative of carburetor maladjustment or malfunctioning of other components within the indLiction system. In the loaded emissions test. the exhaust gas is analyzed for CO and HC using a tail pipe concentration measurement during idle operating conditions and with the engine under load. Vehicles are operated on a chassis dynamometer during this test. Vehicles with excessive emissions are required to undergo maintenance. This test normally produces more information useful in identifying high emitters than the idle test. For example, the frequency of misfire, resulting in excessive HC emissions. is much greater at high load. Presently available data indicate that a program of annual I M can achieve reductions in automobile exhaust emissions of 1 0 % CO and 11% HC i f an idle test is used. and 12% CO and 1 5 % HC if a loaded test is used. In addition, I M reduces fuel consumption by approximately 2%. I M does not significantly affect NO, emissions. How much does it cost?
The investment c:ost of an annual I M program is about $2 per car if an idle test is used, and $3 per car with a loaded test. The cost of inspection is about $1.50 per car per year for either test. Maintenance costs for vehicles that fail the emissions test are typically about $25. However. not more thaii 50% of the cars inspected are normally expected to fail an emission test. Moreover. most cars receive some voluntary maintenance during a year. As a result, the increase in the average car's annual maintenance cost due to I M is expected to be about $3. I M programs using idle tests are now in operation in New Jersey and Chicago. Retrofit Devices that may be added or modifications that may be made to in-use automobiles for the purpose of reducing their emissions are called retrofits. Three retrofit approaches are currently under consideration for widespread implementation. In Vacuum Spark Advance Disconnect ( V S A D ) . the
idle air-fuel mixture is made leaner than normal. idle speed is increased, and the vacuum timing advance is made inoperative during normal engine operation. This approach is applicable to pre-1968 vehicles (pre-1966 in Calif.). I n Air Bleed to Intake Manifold. an air valve enables the air-fuel ratio to be increased by metering additional air to the intake system. This approach is applicable to pre-1972 vehicles. In Oxidizing Catalytic Converter retrofit. an oxidizing catalyst is installed in the exhaust system. This device requires the use of lead-free fuel and. therefore, is applicable only to vehicles that can operate without excessive engine wear on commercially available lead-free gasoline. Considerable work remains to be done on identifying the specific makes and models of automobiles that fulfill this requirement. At present, EPA estimates that about 75% of 1971-74 vehicles and 2 0 % of 1968-70 vehicles could operate on commercial lead-free fuel and be considered for retrofit catalysts. Starting in model year 1975, new cars will be factory-equipped with catalysts or other equally effective emissions controls. Hence, retrofit for 1975 and later automobiles is not under consideration. The average emissions reductions per vehicle and the costs of the three retrofit approaches are shown (Table 2 ) . All of the retrofits require periodic maintenance, and all function most effectively on vehicles in good operating condition. Therefore, emissions control programs using retrofit should include IM. Of the three retrofit approaches. only VSAD, which is used in the California retrofit program. has been implemented on a large scale. The other approaches are at varying stages of development. and additional woik is needed to firmly establish their effectiveness, durability, applicability, and costs. The air bleed and catalyst effectiveness and cost data (Table 2 ) are based on tests involving fewer than 100 cars and are. therefore. subject to considerable uncertainty. EPA is currently developing procedures to facilitate the further development and testing of retrofits. If no serious developmental difficulties arise. air bleed retrofits should be ready for implementation by 1976 and catalysts by 1977. Lowering total emissions The reductions in total automobile emissions achieveable through I M and retrofit can be illustrated by considering two hypothetical I M and retrofit programs. Program 1 consists of loaded-test I M for all cars and air bleed retrofits for pre-1972 vehicles. Program 2 has loaded-test I M for all cars. air bleed retrofit for pre-1972 vehicles, and catalyst retrofit for 75% of 1972-74 vehicles. The emissions reductions achieved by the two programs in the period 1977-85 are displayed (Table 3 ) . Both programs achieve fuel savings of roughly 2% in all years owing. principally. to the effects of I M. As shown. the effectiveness of both the I M and retrofit programs decreases with time. This is caused by the replacement of retrofitted vehicles with post-1974 vehicles. In 1985, all of the program 1 emissions reductions and 60% of the program 2 reductions are attributable to IM. Retrofit is a short-range approach to emissions control. Volume 8 . Number 9 , September 1974
801
Reducinq automobile use Automobile use and emissions can be reduced by diverting automobile trips to other Inodes Of transportation: Compared to retrofit, this appro2ICh to so. tion has the important advantage that it . . cia1 goals as energy conservation, reduced noise ana congestion, and reduced need for further highway construction, in addition to improving air quality. The diversion of automobile driver trips to the two most readily available alternative modes, bus transit and carpools, is considered here. Transit ridership is determined by the relative quality of service provided by transit and the automobile. The most important service variables involve travel times and costs. An example of the quantitative relationship between the service variables and transit ridership for work trips is shown (Figure 2). This example is based upon the results of a study of travel behavior in Pittsburgh. Pa. The service variables included in the figure are the time to walk to and from the transit stop, the difference between automobile and transit travel times, and the difference between automobile and transit costs. The importance of
Most transit systems in the U.S. do not provide the high-quality service needed to attract a high ridership. For example. nearly 50% of ur ban area residencies are located three or more blocks from the nearest transit stop. Transij routes are heavil!I downtown oriented, but ^ I +.in^^ v^"I.. r , l y ^I.^.,+ ,no/ Iv,y L , , w . , y u ,,mtown. Transit trips take nearly twice as long as automobile trips. Moreover, subsidized free or reduced rate parking confers a cost advantage on the automobile. Transit service of this quality is illustrated by point D of Figure 2. Ridership is 4%. Methods of improving transit service include priority treatment of buses on streets and freeways, increased use of limited-stop and express service, better collection and distribution systems to reduce walk distances and travel times, increased schedule frequencies, and increased crosstown and suburban service. In addition, automobile user charges can be increased or parking limitations can be imposed to compensate for the provision of free parking. Such restrictions of automobile use will also compensate for the improvement in automobile service quality that will occur as the diversion of automobile drivers to transit reduces or eliminates traffic congestion.
The attraction of large numbers of work trips from the automobile to transit will also require substantial expansions of bus fleets. For example, to accommodate the travelers displaced by a 10-20% reduction in auto use that is achieved primarily through diversion of work trips, fleet expansions varying from 5 0 % to over 300%, depending on the city involved, may be required. The cost of bus transit depends on the detailed characteristics of the bus system, notably on vehicle occupancies. Buses cost roughly $1.00 per mile to operate compared to $0.07 per mile for cars. A transit system that carries 40 riders per vehicle round trip costs about the same as the commuter automobile. With lower occupancies, costs can increase by as much as $900 per rider per year. Higher occupancy systems, however, could save $100 per rider per year relative to the cost of continued automobile operation. Thus, transit offers the possibility of achieving reductions in automobile emissions at a net cost saving i f transit systems can be designed and operated so as to achieve both high vehicle occupancies and high-quality service over large portions of urban areas.
Carpooling Even under the best of conditions, the diversion of large numbers of automobile drivers to transit is likely to require at least three years owing to the delays involved
in acquiring new vehicles and modifying operating policies. However, moderate reductions in automobile use can be achieved very quickly through the use of carpools. Average automobile occupancy in the U.S. is about two persons per car. Average occupancy for work trips is about 1.4 persons per car. Since most cars are capable of carrying at least four persons, there is considerable room for reducing automobile use and emissions through carpooling. The principal obstacle to carpooling is that carpools are highly restrictive in terms of the service offered. Carpoolers must have trip origins and destinations that are close to one another, must desire to travel at the same times of day, and, to minimize the problems of locating carpool partners, must make trips that are repetitive from day to day. As a result, the greatest potential for increased carpool use is in connection with peak period work trips. These trips are responsible for about 25% of urban area automobile emissions. Experience to date with carpool programs indicates that policies to encourage carpooling, such as locator systems combined with parking priorities, can double automobile occupancies for downtown peak period work trips. These trips cause roughly 1 0 % of automobile emissions in cities. Much more limited expe ience with carpooling for nondowntown peak period work trips suggests that carpool programs can increase automobile occupan-
Volume 8, Number 9, September 1974
803
16 25
0 0
12 20
9
15
0 0
cies for these trips by 10-50%. If these preliminary indications are confirmed by future experience, then programs to encourage carpooling should be capable of reducing total urban area automobile emissions by 5-1 0%. Carpool programs appear capable of achieving net cost savings. A carpool program for the Washington, D.C., area based on a locator system and parking restrictions is estimated to require an initial investment of $1.3 million and to have operating costs of $0.6 million per year. I f this system achieves a 3% increase in automobile occupancies for peak period downtown work trips, the savings it achieves in automobile operating costs will equal the annualized cost of the system transportation control plans Such plans are now in effect in 27 of the 30 AQCR s that require transportation controls, and plans are being developed for the other three. The automobile emissions reduction measures included in these plans are shown (Table 4 ) . I M is included in 25 plans retrofit in 20, carpools or transit improvements in 22, and automobile restrictions in 20 The initial phases of plan implementation are now under way. It is still too early to forecast the speed or success with which the transportation control plans will be imple-
mented. Present law requires that the plans b e fully implemented and that the air quality standards be achieved in all of the affected AQCR's by 1977. However, as indicated in the previous discussion, there is still considerable uncertainty as to both the effectiveness and cost of most of the measures included in the plans. Many of these uncertainties can be resolved only through widespread experimentation with the various measures. Moreover. in some heavily polluted AQCR's, the achievement of the automobile-related air quality standards by 1977 requires traffic curtailments that would severely disrupt economic and social activity. Because of these difficulties, the EPA is seeking an amendment to the Clean Air Act that would provide for more flexibility in the deadlines for achieving the automobile-related air quality standards without sacrificing the need to attain the standards as rapidly as possible. I n addition to eliminating the need for disruptive traffic curtailments, it is hoped that this additional flexibility will facilitate extensive experimentation with transportation control measures. More importantly, it is hoped that scheduling flexibility combined with the requirement for improving air quality as rapidly as possible will encourage the development of an integrated transportation planning and decision-making framework in which decisions about air quality and decisions about interacting social objectives, such as mobility and energy conservation, can be made together. This framework would enable coincidences and conflicts among objectives to be identified, trade-offs to be made where necessary, and full advantage to be taken of coincidences between air quality objectives and other social objectives. Thus, the present transportation control plans do not signify the end of the automobile emissions problem.
FIGURE 2
Dependence of transit ridership on service quality
Walk time = 5 min
Walk;time = 10min
Walk time
=o
Walk time = 5 min WalkI time = 10min 3
Transit Time-Auto Time (min.)
#04 Environmental Science & Technology
TABLE 4
Summary of transportation control plans Transit imPl0Yernents AQCR
I/M
Baltimore Beaumont Boston Chicago Cincinnati Dallas Denver Fairbanks Fresno Houston Indianapolis Las Vegas Los Angeles Minneapolis New York City Phoenix Pittsburgh Philadelphia Portland, Ore. Rochester, N.Y. Sacramento St. Louis Salt Lake City San Antonio San Diego San Francisco Seattle Spokane Springfield, Mass. Washington, O.C.
0
Total
. 0
Retrofit
. . . . . .
andlor
CarpoOIs
0
Auto restrictions 0
Plan being developed 0 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Plan being developed
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 0
0
0
0
Plan being developed
0
0
0
0
0
0
0
0
0
0
0
0
0 0
0
0
0
0
-
-
20
22
0
~
20
Rather, they represent the beginning of a process of learning to design and manage urban transportation systems in a manner that is consistent with air quality needs as well as other social objectives.
Additional reading "Control Strategies far In-Use Vehicles," Environmental Protection Agency, Office of Mobile Source Air Pollution Control, November 1972. "A Disaggregated Behavioral Model of Urban Travel Demand," prepared by Charles River Associates, Inc., far the Federal Highway Administration under Contract No. FH-11-7566, March 1972. Horowitz, J. L. "Cost-Effectiveness Analysis of Alternative Strategies lor Reducing Emissions from Motor Vehicles," Proceedings of the Third International Clean Air Congress, pp. F35-F36, VFIVerlag GmbH. Dusseldorf, Federal Republic of Germany, 1973. Holmes, J. G., Horowitz, J. L., Reid, R. O., Stolpman, P. M., "The Clean Air Act and Transportation Controls: An EPA White Paper," U S . Environmental Protection Agency, Office of Air and Water Programs, August 1973. Kain, J. F., "How to Improve Urban Transportation at Practically No Cost," Public Policy, VoI. XX, No, 3 pp 335-58, Summer 1972. Joel L. Horowitz is a senior research analyst in the Office o f Policy Analysis at €PA. His primary interests are in the area of transportation ContrOlS. His work has included cost-effectiveness analyses of mechanical approaches to reducing in-use vehicle. emissions and studies of the air quality improvements that could result from n e w approaches to the design and management o f urban transportation systems.
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