Automobile air emissions are a well-recognized problem and have been subject to considerable regulation. An increasing concern for greenhouse gas emissions draws additional considerations to the externalities of personal vehicle travel. This paper provides estimates of the costs for automobile air emissions for 86 U.S. metropolitan areas based on county-specific external air emission morbidity, mortality, and environmental costs. Total air emission costs in the urban areas are estimated to be $145 million/day, with Los Angeles, California, and New York City (each $23 million per day) having the highest totals. These external costs average $0.64 per day per person and $0.03 per vehicle mile traveled. Total air emission cost solely due to traffic congestion for the same 86 U.S. metropolitan areas was also estimated to be $24 million per day. These estimates are compared with others in the literature and are found to be generally consistent. These external automobile air emission costs are important for social benefit and cost assessment of transportation measures to reduce vehicle use. However, this study does not include any abatement costs associated with automobile emission controls or government investments to reduce emissions such as traffic signal setting.

Reducing greenhouse gas emissions (GHG) is an important social goal to mitigate climate change. A common mitigation paradigm is to consider strategy "wedges" that can be applied to different activities to achieve desired GHG reductions. In this policy analysis piece, we consider a wide range of possible strategies to reduce light-duty vehicle GHG emissions, including fuel and vehicle options, low carbon and renewable power, travel demand management and land use changes. We conclude that no one strategy will be sufficient to meet GHG emissions reduction goals to avoid climate change. However, many of these changes have positive combinatorial effects, so the best strategy is to pursue combinations of transportation GHG reduction strategies to meet reduction goals. Agencies need to broaden their agendas to incorporate such combination in their planning.

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This paper considers the cost-effectiveness of LEED certified brownfield developments as a vehicle miles traveled (VMT) and greenhouse gas (GHG) emission reduction strategy in comparison with other VMT and GHG reduction alternatives. While residential brownfield developments can be significantly beneficial in reducing VMT and GHG emission, adding LEED transportation credits to these developments results in marginal benefits. Compared with conventional greenfield developments, residential brownfield developments can reduce VMT and its consequential environmental costs by about 52 and 66 percent respectively. LEED certified residential brownfield developments that qualify for the applicable LEED transportation credits can have an additional 0.03% to 3.5% GHG reduction compared with conventional greenfield developments. Implementation and documentation costs of LEED criteria can have a potential negative impact on the cost savings of LEED certified brownfield developments. In addition, LEED transportation criteria are implemented by developers, while the residents benefit from the savings (i.e., time, fuel and maintenance). Society benefits from the reduced external environmental costs. To bridge the gap between costs incurred by the developers and benefits gained by the society and residents, governments can play a significant role by providing incentives. Furthermore, results show that with minimal implementation cost incurred by transportation authorities (about 75 to 95 percent less than other VMT reduction strategies), brownfield developments as well as LEED certified brownfield developments that have earned VMT reduction points can be a beneficial travel demand strategy and an environmentally viable option to assist federal, state, and local governments with their greenhouse gas emission reduction goals. Results of this study show that effective collaboration between transportation and environmental agencies to select those brownfield sites with the highest cost saving potentials can assure a favorable outcome when it comes to decreasing VMT and GHG emissions. Furthermore, providing incentives and guidance to private developers of brownfields can expedite attainment of the VMT and GHG reduction goals set by the public sector.

Some insight into the benefits of regularly and frequently maintaining traffic signal timings within and across jurisdictional boundaries is provided. The rapidly growing Cranberry Township located at the crossroad of two interstate highways (Pennsylvania Turnpike (I-76) and I-79) in the state of Pennsylvania, twenty miles north of Pittsburgh is used as a case study. Environmental and economic costs due to the absence of monitoring and updating traffic signal timings are estimated. While traffic signal timing optimization and coordination is a cost effective strategy to reduce travel time and its consequential air emissions along corridors, implementing such timing plans are only effective at and around the time of implementation, while travel demand remains constant. As times passes, with the fluctuation of vehicular demands, especially in rapidly developing areas, timing plans need to be monitored and modified. In Cranberry Township such developments and travel demand fluctuations result in significant increase in costs of travel (time and fuel) and external environmental costs. Estimates show that timing plans that were at their optimal level at the time of implementation, in less than two years result in 18 percent increase in the cost of fuel, 13 percent increase in the cost of travel time and 11 percent increase in the external environmental costs, if left unmodified.