1

Introduction

The Clean Air Act Amendments of 1990 (CAAA) (Public Law 101-549, 42 U.S.C. 7401, et seq.) and complementary provisions of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) (Public Law 102-240, 49 U.S.C. 101 note) tightened controls on the transportation sector to help ensure that transportation activities contribute to timely attainment of national health standards for air quality. As a result traditional transportation projects, such as additions to highway capacity, have come under close scrutiny as potential contributors to air pollution.

For years transportation officials have relied on adding highway capacity—building new expressways and adding lanes to existing freeways —to accommodate travel demand in growing metropolitan areas. Such increases in capacity were thought not only to bring congestion relief but also to improve air quality and fuel efficiency by contributing to freer-flowing traffic conditions.

This conventional wisdom has been challenged by environmental planners and other analysts who take a long-term perspective on the



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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use 1 Introduction The Clean Air Act Amendments of 1990 (CAAA) (Public Law 101-549, 42 U.S.C. 7401, et seq.) and complementary provisions of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) (Public Law 102-240, 49 U.S.C. 101 note) tightened controls on the transportation sector to help ensure that transportation activities contribute to timely attainment of national health standards for air quality. As a result traditional transportation projects, such as additions to highway capacity, have come under close scrutiny as potential contributors to air pollution. For years transportation officials have relied on adding highway capacity—building new expressways and adding lanes to existing freeways —to accommodate travel demand in growing metropolitan areas. Such increases in capacity were thought not only to bring congestion relief but also to improve air quality and fuel efficiency by contributing to freer-flowing traffic conditions. This conventional wisdom has been challenged by environmental planners and other analysts who take a long-term perspective on the

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use effects of additional highway capacity. They concede that adding highway capacity may initially reduce some vehicle emissions and improve fuel efficiency by smoothing traffic flows and reducing stop-and-go traffic, although the benefits may not be as significant as were once believed. However, these positive effects may be eroded over time by growth in travel stimulated by the new capacity. Improved levels of highway service may encourage shifts from less polluting modes of transportation and induce new or longer trips once discouraged by congested conditions. As traffic volume grows, traffic operations may deteriorate, producing levels of congestion comparable with previous conditions but at higher traffic volumes. In the long run, these analysts maintain, new highway capacity will improve access and may encourage development in low-density areas not amenable to transit. Low-density development requires more frequent and longer trips, increasing emission levels and energy use and further degrading air quality. The issue of highway capacity and air quality is already at the center of legal challenges brought by environmental groups to many additions to highway capacity in metropolitan areas. This issue is likely to receive more attention as metropolitan areas grapple with the stricter requirements of the CAAA. The act allows citizen suits to be brought for the first time against the U.S. Department of Transportation (DOT) and the Environmental Protection Agency (EPA) for noncompliance with legislative requirements and timetables, which opens the door to increased litigation. Assessment of the precise consequences for air pollution and energy use of any particular addition to highway capacity is uncertain, given the current state of knowledge and modeling practice. Travel demand forecasting models—the basis for determining the effect of increased highway capacity on travel demand—were originally developed to help determine the appropriate size of new capital facilities. They are not well suited to providing the detailed data, such as speed data and travel data by time of day, needed for modeling and analysis of vehicle emissions and air quality impacts. Nor can most current travel demand models adequately measure the effect of improvements in highway service on the amount of travel or on land use patterns, which in turn could affect future demand for travel and its distribution in a region. Emissions models, which measure the polluting effects of motor vehicle travel, inadequately represent the emission performance of

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use in-service vehicles. Current data on the relationship between vehicle speeds and emission levels—critical to analyzing highway capacity projects that will change the distribution of traffic speed levels and variability of speeds—are based on averages that mask wide variances across individual vehicle performance, roadway conditions, and driving behavior. Moreover, the models do not adequately capture major suspected sources of emissions from vehicle accelerations and high speeds, although some research is under way to understand these phenomena. Planning agencies often apply current speed-emission relationships as if they were precisely known. Despite the limitations of the existing knowledge base, engineers and scientists are being pressed to provide reliable estimates of the likely effects of adding highway capacity on emissions and energy use to assist legislators, state officials, metropolitan planning organizations (MPOs), and judges in reaching decisions on these issues. Thus a review of the current state of knowledge has been undertaken to evaluate the scientific evidence concerning these effects and to narrow areas of disagreement. The specific questions at issue are described and, where possible, research or analyses that could be conducted to speed their resolution are recommended. More specifically, the study committee Critically reviews existing research of the links among highway capacity, traffic flow characteristics, travel demand, land use, vehicle emissions, air quality, and energy use in metropolitan areas; Identifies the conditions most likely to affect emissions and energy use; Reviews the reliability of models and analyses that regional and state planning agencies use to forecast travel demand and land use, emission levels, and energy consumption; and Recommends research strategies, modeling improvements, and data collection efforts to improve analytic capabilities. REGULATORY CONTEXT The enactment of the CAAA has refocused attention on the effects of transportation activity on air quality, but legislation to set standards for alleviating air pollution and improving the fuel efficiency of motor vehicles dates back to the 1970s.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use Clean Air Legislation and Regulatory Requirements The harmful effects of air pollution on public health were formally recognized by the requirements of the Clean Air Act Amendments of 1970 (Public Law 91-604, 84 Stat. 1676), which mandated establishment of national ambient air quality standards (NAAQS) for six pollutants: carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulates (PM-10), and sulfur dioxide (SO2) (Curran et al. 1994, 19). There is no standard for carbon dioxide, the principal greenhouse gas, because carbon dioxide is not toxic and therefore has no direct negative health impact. Historical Trends Since 1970 substantial gains have been made in reducing pollution from transportation sources, primarily through technological improvements such as catalytic converters and electronic fuel injection, which are now standard equipment on cars,1 and through the use of lead-free gasoline. Between 1970 and 1993, for example, highway vehicle emissions of CO and volatile organic compounds (VOCs)2 (which are a precursor of ozone) declined by 32 percent and 53 percent, respectively; highway vehicle emissions of lead were effectively eliminated (Nizich et al. 1994a, 3-11, 3-13, 3-16; Figure 1-1). However, highway vehicle emissions of nitrogen oxides (NOx)—the other ozone precursor—remained nearly constant (Nizich et al. 1994a, 3-12).3 Although the emissions models on which these estimates are based typically have underestimated absolute emission levels, the trend has been downward. Despite more than two decades of progress in improving air quality, EPA estimated that in 1993 about 59 million people lived in counties that violated one or more of the NAAQS (Curran et al. 1994, 14). 4 Thus, the CAAA contain stringent requirements for further reductions in emissions from transportation sources, backed up by strict monitoring and sanctions for nonperformance, to bring nonattainment areas (i.e., those areas not attaining NAAQS) into compliance.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use FIGURE 1-1 Highway vehicle emissions of selected pollutants: 1970, 1980, and 1993 (Nizich et al. 1994a, E-11–E-13). Requirements of the 1990 CAAA The act requires additional technological advances, such as tougher tail pipe standards, enhanced vehicle inspection and maintenance programs, and cleaner fuels programs, which should result in further reductions in emissions as newer, cleaner vehicles replace older ones and as technology-oriented programs are implemented. These measures, however, may not offset growth in emissions from motor vehi-

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use cle travel. For example, if vehicle miles traveled (VMT) grows at a relatively conservative rate of 2 percent per year5 and no additional technology advances are made other than those included in the CAAA, EPA estimates that tail pipe emission gains could be offset by 2002 for CO and VOC and by 2004 for NOx (Figure 1-2).6 Thus, the CAAA mandate measures to limit automobile trips in the most severely polluted areas and require strict monitoring of VMT growth in less severe nonattainment areas. Deadlines for reaching attainment vary with the severity of air quality problems.7 Areas classified as marginal (40 for ozone) have 3 years from the baseline year, 1990, to attain NAAQS; areas classified as moderate (29 areas for ozone, 37 for carbon monoxide) have 6 years. The 12 areas classified as serious for ozone (and 1 for carbon monoxide) have 9 years, whereas the areas classified as severe (9 for ozone) have 15 to 17 years. Los Angeles, the only area classified as extreme (for ozone), has 20 years. Eighty-three areas have been designated as nonattainment for PM-10. Los Angeles is also the only area that does not meet the NO2 standard. Levels of effort also vary with the severity of air quality problems. Areas with ozone classifications of moderate or worse must submit revisions to State Implementation Plans (SIPs) (plans that codify a state's CAAA compliance actions) showing that within 6 years the pollutants that create ozone will be reduced by at least 15 percent from 1990 baseline emissions net of any growth in emissions during that period. These areas must achieve an additional 3 percent per year reduction in emissions until attainment is achieved. In addition to the latter requirements, areas classified as severe or extreme must adopt transportation control measures (TCMs) aimed at decreasing automobile travel.8 Areas with carbon monoxide designations only, of moderate or worse, must comply with somewhat different requirements. They must forecast VMT annually beginning in 1992, and if actual VMT exceeds forecast, they must be ready to adopt contingency TCMs that must be included in SIPs. TCMs are required for carbon monoxide areas designated as serious. Finally, the CAAA provide strict sanctions for noncompliance. For example, approval of federally assisted highway projects can be withheld for failure to submit a SIP, EPA disapproval of a SIP, failure to

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use make a required submission, or failure to implement any SIP requirement. 9 Once such sanctions have been imposed—and they must be imposed if EPA determines that the deficiency has not been corrected 18 months after being identified—DOT can only approve highway safety projects or projects that would not increase single-vehicle automobile travel.10 Conformity Requirements The requirements and timetables for meeting CAAA goals and sanctions for noncompliance are stringent, but not unlike mandates of earlier clean air legislation (e.g., in 1970 and 1977). To help ensure attainment of legislative mandates, regulations implementing the 1990 CAAA strengthen existing conformity requirements. Conformity is a determination made by MPOs and DOT that transportation plans, programs, and projects in nonattainment areas are in accord with the compliance standards contained in SIPs (FHWA 1992b, 12). The new conformity rules under the CAAA hold MPOs and DOT directly accountable for demonstrating that transportation activities will not cause or contribute to any new violation of air quality standards, increase the frequency or severity of existing violations, or delay timely attainment of standards (Federal Register 1993b, 62,188). EPA regulations provide a grace period for states to revise their SIPs; revised plans were due November 1994. However, stringent interim conformity guidelines are in effect until EPA has approved these plans to ensure that nonattainment areas do not fall behind in meeting target deadlines for achieving air quality standards. The salient feature of the interim conformity process is project-level review. Specifically, MPOs in nonattainment and maintenance areas must show that (a) all federally funded and “regionally significant projects,” including nonfederal projects,11 in regional transportation improvement programs (TIPs) and plans will not lead to emissions higher than in a 1990 baseline year; and (b) by building these projects, emissions will be lower than if the projects are not built. Once SIPs are approved by EPA,12 the conformity test becomes less demanding: MPOs must demonstrate through a regional analysis that the emissions produced by implementation of transportation plans and TIPs will not exceed target levels (known as emission

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use FIGURE 1-2 Relationship between travel growth and motor vehicle emissions (data from EPA Motor Vehicle Emission Laboratory, 1994).

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use budgets)13 for motor vehicle emission sources from nonattainment and maintenance areas contained in the SIPs. The conformity regulations thus provide the teeth to help guarantee compliance with air quality mandates. MPOs must reconcile emission estimates from transportation plans and TIPs with those contained in the motor vehicle emission budgets in SIPs, conduct periodic testing to determine whether actual emissions are in line with estimates, and take remedial action if they are not. Court challenges have already been issued by environmental groups against several state transportation departments to ensure that conformity requirements and attainment deadlines are met.14 ISTEA ISTEA complements the CAAA by reinforcing air quality conformity requirements. The act allows local areas flexibility to shift highway funds to transit and other cleaner modes, enhances the planning re-

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use sponsibilities of MPOs that are responsible for conformity analyses, and creates a new Congestion Mitigation and Air Quality Improvement Program to direct funds to projects and programs in nonattainment areas that will contribute directly to attainment of the NAAQS (FHWA 1992c, 16–17). Metropolitan transportation planning regulations, in particular, were revised in part to ensure greater consistency and coordination between development of transportation and air quality plans (Federal Register 1993c).15 Energy Regulation Legislation similar to the CAAA has not been passed recently in the energy area. In response to the oil embargo imposed by the Organization of Petroleum Exporting Countries (OPEC) in 1973 and because the automotive sector is a major consumer of petroleum, Congress passed the Energy Policy and Conservation Act of 1975, which set fuel economy standards requiring that automotive manufacturers increase the corporate average fuel economy (CAFE) of automobiles and light trucks sold in the United States to 11.7 kpl (27.5 mpg) in the 1985 model year and thereafter (NRC 1992, 12). Between 1970 and 1992, in-use fuel economy for passenger cars rose from an average of 5.7 kpl (13.5 mpg) to 9.2 kpl (21.6 mpg), a 60 percent improvement (Davis 1994, 3–24). The introduction of CAFE standards, technology improvements such as electronic fuel injection and more efficient engines and transmissions, and the reduced weight of passenger vehicles were largely responsible. Although the standards have been achieved,16 during the past decade the low price of gasoline, growing motor vehicle ownership, and increased motor vehicle travel have resulted in a steady increase of transportation's share of total petroleum consumption in the United States to 65 percent in 1992 (Davis 1994, 2–7). Also, other sectors have substituted alternative energy sources. Since 1989, U.S. energy dependence on foreign oil sources has reached levels only exceeded in 1979; oil imports accounted for 46 percent of U.S. petroleum consumption in 1992 (Davis 1994, 2–5). Thus, energy officials are seeking ways to improve fuel efficiency and reduce vehicle travel to cut back energy consumption.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use STUDY FOCUS The conformity requirements of the CAAA and, to a lesser extent, concern for energy use will place transportation projects—particularly highway projects in the nation's most polluted areas—under great scrutiny regarding their potential for stimulating automobile travel, raising emission levels, and further increasing dependence on fossil fuels. Local planning agencies, who are responsible for programming highway projects in urban areas and certifying their positive or neutral effects on air quality, are expected to have the analytic and modeling capabilities to forecast project impacts. Such requirements provide the impetus and the focus for this study. The committee did not limit its examination of the effects of highway capacity additions to a specific time frame. However, particular attention was paid to the 20-year time frame established by the CAAA for attainment of air quality standards, because this represents the planning and forecasting horizon within which local planning agencies must make decisions about the air quality effects of highway projects. The size of the investment in capacity enhancements also warrants close examination of potential impacts. Although construction of new highways has tapered off in recent years, the combination of new construction with capacity additions to existing highways continues to represent a large fraction of the public investment in transportation infrastructure by state and local governments. For example, according to the most recent estimates, capacity improvements to roads and bridges totaled $15.4 billion,17 accounting for nearly two-fifths (38 percent) of total public capital outlays for highways, bridges, and transit combined (U.S. Congress. House. Committee on Public Works and Transportation. 1993, 4, 76). Alternative ways of meeting urban transportation needs are not examined in this study, nor are the costs and benefits of alternative approaches to improving air quality and reducing energy use in a metropolitan region analyzed. Instead the study is focused on examining the scientific basis for estimating the impacts of highway capacity enhancement projects, both favorable and unfavorable, on emissions, air quality, and energy consumption.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use sources of emissions, interact with vehicle emissions to affect regional air quality. The primary objective of this study is to examine how an increasein the supply of highway facilities affects each of these factors (Figure 1-3). Initial impacts involve a change in traffic flows on the affected links (e.g., changes in the distribution of vehicle speeds, changes in speed variation, and shifts in traffic volumes) and the resulting change in emissions and energy use from the vehicles on those links. Over time the effects could involve a change in the amount of travel and in land use patterns, with corresponding effects on emissions and energy use, as households and businesses react to the network addition. The incremental effects of all these changes on emissions, air quality, and energy use must be estimated to determine the full effects of the capacity increase. There is both a spatial and a temporal dimension to these analyses. A change in supply may involve adding capacity and improving traffic flow at only one location on the highway system. However, the network character of the system is likely to affect travel patterns at other locations. Traffic may be diverted from alternate routes, or travelers may shift their time of travel to preferred travel times to take advantage of the new capacity or change their mode of travel if they are encouraged to reduce automobile trips by using transit or bicycle or by walking. If the addition to capacity is sufficiently large, it can induce new or longer trips, influence automobile purchasing decisions, and cause residents or businesses to change their location to take advantage of the improved access. Similarly, emissions from these changes are not confined to the location of the project, but depending on local atmospheric conditions (e.g., heat and wind patterns) may have broader effects on the air quality of the region and beyond. Individual highway projects may not have measurable effects on regional air quality, but the cumulative impacts of many projects could. Thus, whereas a highway capacity enhancement project may be localized, its effects are unlikely to be. Project impacts will change over time. If a highway capacity addition stimulates travel demand or encourages dispersed development patterns, these outcomes will erode initial gains from some capacity projects. However, some of these impacts, such as decisions about changes in the location of residences and businesses and the traffic

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use generated by these changes, are likely to take place over a period of years or even decades. Assessing the net effects of highway capacity projects on emissions and energy use depends on the length of time over which impacts are analyzed and how the flow of future effects is valued (i.e., discounted back to the present). Examination of project effects at a single point in time is misleading. The size and direction of the effects and the certainty of the predictions depend on several factors. The context in which the capacity enhancement is made is critical: whether existing highways are heavily congested and travel demand is constrained; whether the area is heavily developed and thus the potential for growth is limited; or, conversely, whether the area is relatively undeveloped but conditions for growth are present and thus the rate of growth in development and related traffic is likely to be accelerated. Each of these conditions will result in different project outcomes for travel behavior, land use, and urban form. The scale of effects also depends on the unit of analysis. Highway capacity additions may have significant effects on travel patterns and development activity in a particular corridor or subregional area. However, the effects may be small at the regional level, at least in the 20-year planning horizon required for metropolitan transportation planning and conformity purposes.19 Highway capacity additions represent small increments to large existing metropolitan transportation networks and to land use patterns that have evolved over many years. The type of project also matters. For example, minor capacity improvements on arterials—such as signalization improvements and exclusive turn lanes—may smooth traffic flows, initially reducing emissions and energy use, without major offsetting increases in motor vehicle traffic. 20 However, the size of the benefits will be commensurate with traffic levels on these local routes and may have little measurable impact on regional air quality. A series of relatively minor traffic flow improvements can have a cumulatively larger impact on motor vehicle traffic growth. Major capacity enhancement projects, such as a new freeway or a major new bypass, are likely to have more significant initial effects on emissions and energy use (although effects can be negative as well as positive). They may have adverse effects in the longer term because of increased motor vehicle travel stimulated by the project.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use The effects of not adding highway capacity also must be considered in any assessment of net effects on highway emissions and energy use. Is there sufficient capacity in the existing highway network for travelers to change routes and times of travel without significantly adding to highway congestion levels and thereby increasing emissions and energy use? Can other investments in transit facilities or bikeways provide alternative modes of transport with sufficient incentive for travelers to switch from automobile travel to keep highway congestion from growing? If highway congestion increases, will residents and businesses respond by moving to less congested suburban or exurban areas or to smaller, less congested metropolitan areas? Or will congestion simply become worse, making the capacity addition more valuable in the future relative to the no-build option? Finally, the level of certainty of the predictions will vary. Forecasts of emissions resulting from the initial adjustments in traffic flows and travel patterns because of a highway capacity project should be relatively straightforward, although technical issues involved in modeling vehicle emissions and systems issues (i.e., route shifts and changes in time of travel) must be addressed. Forecasting longer-term effects such as shifts in travel demand and land use changes from capacity additions is more complex and requires predicting behavioral responses that are not fully understood. The longer the time horizon for estimating impacts, the more other, often unpredictable, factors such as changes in demographic or economic conditions are likely to intervene, reducing the ability to forecast accurately. ASSESSMENT OF IMPACTS The difficulty of reaching consensus on the direction and size of effects was demonstrated in a recent court case filed in 1989 by the Sierra Club Legal Defense Fund and Citizens for a Better Environment against the Metropolitan Transportation Commission (MTC), the MPO for the San Francisco Bay Area (U.S. District Court 1990a).21 Environmental groups sued MTC for noncompliance with the obligations contained in the Bay Area's 1982 SIP to meet federal air quality standards by 1987. A major issue of the court case concerned the extent to which large highway capacity expansions would adversely affect regional air qual-

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use ity and MTC's capacity to model and analyze these impacts. Court testimony by experts provides a good summary of the key arguments put forward by local planners and modelers, environmental groups, theoreticians, and practitioners concerning the effect on air quality of increased highway capacity. Environmental groups argued that adding highway capacity in a congested system would increase vehicle use by making automobile travel easier and more convenient, thereby offsetting at least some of the initial reduction in emissions from smoothing traffic flows.22 Specifically, drivers respond to improved levels of highway service by concentrating work trips more in traditional peak periods; shifting from transit and higher vehicle occupancies to automobile and lower, or single, vehicle occupancies; taking more individual trips rather than combining trips (trip chaining); and taking longer trips or trips that might otherwise have been forgone, ultimately producing levels of congestion comparable with previous conditions but at higher traffic volumes. In the long run, the argument continued, adding highway capacity in a congested system would encourage further decentralization of households and jobs and longer commuting by making travel to outlying areas easier and faster. Because most major highway capacity investments are being made in suburban areas, these projects would change the distribution of development within the region; low-density, automobile-dependent development at the suburban fringe would be encouraged over redevelopment of core areas that could better support public transit and nonmotorized travel modes. Moreover, if highway transportation investment stimulates economic growth, as project proponents frequently claim, then capacity enhancements should increase overall levels of regional growth, drawing new jobs and households to the area and making it even more difficult for the region to meet environmental standards. Those who supported the MTC argued that capacity additions under most conditions would result in emission reductions and greater fuel efficiencies from freer-flowing traffic.23 They conceded that adding highway capacity could increase the number and length of trips and that in the long run this could increase levels of automobile ownership and affect the location of population and housing in the region. However, given the scale of most highway projects in the built environment of major metropolitan areas, they argued that adding

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use new highway capacity should not induce new travel at levels that would overwhelm initial emissions and energy benefits. Moreover, they said, there is no empirical support for the proposition that highway capacity additions in regions that are already substantially developed make a measurable difference in overall levels of population or employment growth. Transportation is not the primary determinant of regional development; business and residential location decisions are based on a host of factors (e.g., national and regional economic conditions, local labor force skills, tax levels, and public services) of which transportation is one, but not the major, factor. Thus, providing new capacity would simply accommodate more efficiently the inevitable new development. After 3 years of litigation, the court found that MTC's adoption of additional TCMs met the “reasonable further progress” requirement toward emission reductions outlined in the Bay Area's 1982 SIP (U.S. District Court 1992). In addition, the court ruled in favor of MTC's proposed modified computer modeling techniques for conformity assessment and lifted a temporary ban on several highway expansion projects (U.S. District Court 1991c). The judge did not require MTC to determine whether the new highway capacity would contribute to regional growth and increase total pollution levels, arguing that EPA has not yet made this a requirement and that the capability to model this relationship does not currently exist (U.S. District Court 1991c). ORGANIZATION OF REPORT These issues are explored more systematically in the following chapters. Background information on the effects of motor vehicle transportation on air quality and energy consumption is given in Chapter 2, and the main analytic tools used to model these effects are introduced. The impacts, both initial and long term, of additions to highway capacity on traffic flows, travel demand, and land use and urban form are examined in Chapter 3, Chapter 4 through Chapter 5, respectively. In each area, what is known from theory, empirical studies, and statistical models is summarized; an assessment of the validity and certainty of the evidence is provided; and recommendations are made for improving the state of knowledge. In Chapter 6, major findings about the relationships between highway capacity additions, emissions, air quality, and

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use energy consumption are summarized, highlighting what is known, what is knowable, and what is not, and conclusions are drawn about the current focus and requirements of the CAAA. NOTES 1. Catalytic converters, which control for CO, VOC, and NOx emissions, were introduced in 1978, and carbon canisters, which control hydrocarbon, or VOC, emissions from the fuel system that occur while the car is in operation or while parked by adsorbing the vapors, have been in use since 1975 (NRC 1992, 70). 2. VOCs are also referred to as nonmethane hydrocarbons (NMHC) and as reactive organic gases (ROGs) or total organic gases (TOGs), the terms used in California. 3. Comparative data on emissions from all other sources cannot be provided because the methodologies used to estimate emissions from all sources except highway vehicles changed after 1985. The differences in methodologies result in as much as a 20 percent difference in EPA estimates of CO emission levels in 1985 (Nizich et al. 1994b, 3, 6). Highway vehicle emissions, however, were estimated using a consistent methodology for 1970 through 1993. 4. This population estimate is based on a single year of data and only considers counties with monitoring data for that pollutant (Curran et al. 1994, 14). The data can vary substantially from year to year primarily because of changes in meteorological conditions. 5. VMT has grown at annual rates of 3.5 percent over the past decade (U.S. Congress. House. Committee on Public Works and Transportation. 1993, 37). There is some evidence, however, that future increases in VMT levels may not be as great as in the past because of saturation in vehicle ownership, aging of the driving population, and the like (U.S. Congress. House. Committee on Public Works and Transportation. 1989, 87–91). 6. EPA estimates assume a small increase in the share of diesel vehicles, particularly heavy-duty diesel vehicles, relative to gasoline-powered light-duty vehicles over the 20-year period (personal communication, Natalie Dobie, Technical Support Branch, EPA, Nov. 21, 1994). 7. The following two paragraphs draw heavily from background material on the impact of highway congestion on air quality prepared by Elizabeth Deakin for TRB in March 1991 (Deakin 1991). Data on nonattainment areas were updated using EPA's 1993 National Air Quality Emissions Trends Report (Curran et al. 1994). 8. TCMs are activities intended to decrease automotive travel or otherwise reduce vehicle emissions. TCMs are most closely associated with actions

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use to improve transit, support ridesharing, and encourage employer-based trip reduction programs (FHWA 1992a, 3–4). 9. In a Notice of Proposed Rulemaking (Federal Register 1993a), EPA proposed an automatic sanctioning procedure. An EPA finding of noncompliance by a state regarding its SIP would trigger an 18-month clock for the imposition of a two-for-one mandate for industrial emissions, requiring an offset of twice the increased emission from a new or modified point source. If the SIP remains deficient after another 6 months, EPA would then cut off federal highway funds. 10. Such projects include transit, HOV lanes, employee trip reduction programs, emission-reducing traffic flow improvements, fringe parking, pricing programs to restrict vehicle use, and accident management programs. 11. Regionally significant projects include any facility with an arterial or higher functional classification and any other facility that serves regional travel needs and that would normally be included in the modeling for the transportation network (Federal Register 1993b, 62,211). Projects that are not regionally significant must also be included in regional emissions analyses, but the effects of these projects, which cannot normally be modeled with a transportation network demand model, may be estimated in accordance with reasonable professional practice (Federal Register 1993b, 62,211). Finally, nonfederal regionally significant projects must have been included in a conforming plan or TIP, or included in the original regional emissions analysis supporting the adoption of the plan or TIP, or a new regional emissions analysis must demonstrate that the plan and TIP would still conform if the projects were included and implemented (Federal Register 1993b, 62,204). 12. During the period after SIPs have been submitted but have not been approved by EPA, MPOs must demonstrate that TIPs pass the build –no-build test and also that the build scenario does not exceed the emissions budget for motor vehicle emissions contained in the submitted SIP (Federal Register 1993b, 62,191). 13. Motor vehicle emission budgets are the motor vehicle-related portions of the projected emission inventory used to demonstrate reasonable further progress milestones, attainment, or maintenance for a particular year specified in a SIP. They establish a cap on emissions that cannot be exceeded by predicted highway and transit vehicle emissions (Federal Register 1993b, 62,194). 14. Six environmental groups filed notice of their intention to sue the transportation departments of New York, New Jersey, and Connecticut for approving transportation improvement programs that fail to meet the 1990 CAAA pollution reduction requirements (AASHTO Journal 1992, 3–4); suits have been filed against Connecticut and Rhode Island (AASHTO Journal 1993, 7–9). The Environmental Defense Fund and other groups

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use have already brought suit against EPA and DOT to force issuance of various regulations associated with the legislation. 15. For example, among other provisions, metropolitan transportation plans must cover a period of at least 20 years, contain all regionally significant projects, consider the likely effect of transportation policy decisions on land use and development, and, for nonattainment or maintenance areas, contain only conforming projects (Federal Register 1993c). 16. The sales-weighted fuel economies of automobiles and light trucks have, on average, met the fuel economy standards set by the federal government. This does not mean, however, that each manufacturer is meeting the standards each year. Some manufacturers still fall short, whereas others exceed the standards (Davis 1994, 3–51). 17. This does not include signalization and other traffic flow improvement projects, which are not broken out separately. 18. The time period used in most capacity analysis is 15 min, the shortest interval during which stable flow exists. Capacity is defined for prevailing roadway conditions (which refer to the geometric characteristics of the facility), traffic conditions (which refer to the characteristics of the traffic stream using the facility), and control conditions (which refer to the types and specific design of control devices and traffic regulations on a given facility); good pavement and weather conditions are assumed. 19. ISTEA requires the metropolitan transportation plan to address a period of at least 20 years (Federal Register 1993c, 62,210). 20. To the extent these projects degrade bicycle and pedestrian travel, they may induce some shifts to cars, thus increasing emissions. 21. The lawsuit was filed in the Federal District Court of Northern California. The citation for the consolidated cases is Citizens for a Better Environment et al. v. Peter B. Wilson et al., Civil No. C-89-2044-TEH, and Sierra Club vs. Metropolitan Transportation Commission et al., Civil No. C-89-2064-TEH. 22. The arguments of those who view highway capacity improvements as having a negative effect on air quality are drawn from three sources: (a) background material prepared for TRB by Elizabeth Deakin (Deakin 1991), (b) testimony by Dr. Peter Stopher, Professor of Civil Engineering, Louisiana State University, and Director of the Louisiana Transportation Research Center, in the MTC case (U.S. District Court 1990b), and (c) a paper by Greig Harvey and Elizabeth Deakin (Harvey and Deakin 1991) on regional transportation modeling practice. 23. The arguments of those who view highway capacity improvements as having a positive or neutral effect on air quality are drawn from the background material provided by Deakin (1991), from the Harvey and Deakin 1991 paper, and from the testimony by Elizabeth Deakin, Assistant Professor of City and Regional Planning and member of the research staff of

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use the Institute of Transportation Studies at the University of California, Berkeley (U.S. District Court 1991a), and Dr. Raymond Brady, Research Director for the Association of Bay Area Governments (U.S. District Court 1991b) in the MTC case. REFERENCES ABBREVIATIONS EPA Environmental Protection Agency FHWA Federal Highway Administration NRC National Research Council TRB Transportation Research Board AASHTO Journal. 1992. States May Face Clean Air, ISTEA Suit. Sept. 25, pp.3–6. AASHTO Journal. 1993. Connecticut, Rhode Island Hit with Environmental Suits. March 26, pp. 7–9. Curran, T., T. Fitz-Simons, W. Freas, J. Hemby, D. Mintz, S. Nizich, B. Parzygnat, and M. Wayland. 1994. National Air Quality and Emissions Trends Report, 1993. 454-R-94-026. U.S. Environmental Protection Agency. Research Triangle Park, N.C., Oct. Davis, S.C. 1994. Transportation Energy Data Book: Edition 14. ORNL-6798. Center for Transportation Analysis, Energy Division, Oak Ridge National Laboratory, Tenn., May. Deakin, E. 1991. Scoping Study: Impact of Highway Congestion on Air Quality. University of California at Berkeley, March, 22 pp. Federal Register. 1993a. Application Sequence for Clean Air Act Section 179 Sanctions. Vol. 58, No. 189, Oct. 1, pp. 51, 270–51, 279. Federal Register. 1993b. Criteria and Procedures for Determining Conformity to State or Federal Implementation Plans of Transportation Plans, Programs, and Projects Funded or Approved Under Title 23 U.S.C. or the Federal Transit Act . Vol. 58, No. 225, Nov. 24, pp. 62, 188–62, 253. Federal Register. Part II. 1993c. Statewide Planning. Metropolitan Planning. Vol. 58, No. 207, Oct. 28, pp. 58, 040–58, 179. FHWA. 1992a. Transportation and Air Quality: Searching for Solutions: A Policy Discussion Series. No. 5, FHWA-PL-92-029. U.S. Department of Transportation, Aug., 30 pp. FHWA. 1992b. A Summary: Transportation Programs and Provisions of the Clean Air Act Amendments of 1990. FHWA-PD-92-023. U.S. Department of Transportation, Oct.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use FHWA. 1992c. A Summary: Air Quality Programs and Provisions of the Intermodal Surface Transportation Efficiency Act of 1991. FHWA-PD-92-022. U.S. Department of Transportation, Aug. Harvey, G., and E. Deakin. 1991. Toward Improved Regional Transportation Modeling Practice. Deakin Harvey Skabardonis, Inc., Berkeley, Calif., Dec., 68 pp. Nizich, S.V., T.C. McMullen, and D.C. Misenheimer. 1994a. National Air Pollutant Emission Trends, 1900–1993. EPA-454/R-94-027. Office of Air Quality Planning and Standards, Research Triangle Park, N.C., Oct., 314 pp. Nizich, S.V., W.R. Barnard, and D.Y. Linderman. 1994b. Preparation of a National Emission Data Base for Trends and Other Analyses. EPA and E.H. Pechan & Associates, Inc. Presented at the Emission Inventory Specialty Conference, Air and Waste Management Association, Nov. 1–3, Raleigh, N.C., 12 pp. NRC. 1992. Automotive Fuel Economy: How Far Should We Go? National Academy Press, Washington, D.C., 259 pp. TRB. 1991. Special Report 232: Advanced Vehicle and Highway Technologies. National Research Council, Washington, D.C., 90 pp. TRB. 1992. Special Report 209: Highway Capacity Manual (2nd edition revised). National Research Council, Washington, D.C. U.S. Congress. House. Committee on Public Works and Transportation. 1989. The Status of the Nation's Highways and Bridges: Conditions and Performance and Highway Bridge Replacement and Rehabilitation Program 1989. Committee Print 101-2. Government Printing Office, June. U.S. Congress. House. Committee on Public Works and Transportation. 1993. The Status of the Nation's Highways, Bridges, and Transit: Conditions and Performance. Committee Print 103-2. Government Printing Office, March. U.S. District Court for the District of Northern California. 1990a. Memorandum of Points and Authorities in Support of Revised Conformity Assessment Procedures. Civil No. C-89-2044-TEH and C-89-2064-TEH [consolidated], July 3, pp. 9–10. U.S. District Court for the District of Northern California. 1990b. Declaration of Dr. Peter R. Stopher in Support of Sierra Club's Objections to MTC's Proposed Conformity Assessment. Civil No. C-89-2044-TEH and C-89-2064-TEH [consolidated], Aug. 20. U.S. District Court for the District of Northern California. 1991a. Declaration of Elizabeth Deakin in Support of MTC's Proposed Revised Conformity Assessment Procedure. Civil No. C-89-2044-TEH and C-89-2064-TEH [consolidated], Feb. 25.

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EXPANDING METROPOLITAN HIGHWAYS: Implications for Air Quality and Energy Use U.S. District Court for the District of Northern California. 1991b. Declaration of Raymond J. Brady in Regard to Metropolitan Transportation Commission's Proposed Conformity Assessment Procedures. Civil No. C-89-2044-TEH and C-89-2064-TEH [consolidated], Feb. 26. U.S. District Court for the District of Northern California. 1991c. Henderson Court Order Approving MTC Procedures. Civil No. C89-2064-TEH (Consolidated Cases), March 11. U.S. District Court for the District of Northern California. 1992. Order. Civil No. C89-2064 TEH (Consolidated Cases), May 11.