Background: Together, the Clean Air Act Amendments of 1990 (CAAA) and the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) represented a major step in directly linking statewide and metropolitan transportation planning and development decisions to attainment and maintenance of national air quality standards. An important element of ISTEA is a shift toward flexible intermodal transportation solutions tailored to the specific needs of the state or metropolitan area in both planning and implementation. This policy shift includes the requirement for states and their metropolitan planning organizations (MPOs) to consider transportation of freight as well as people in their decisions on transportation system performance and air quality.

Throughout the last several decades, the United States has experienced a steady and significant growth in heavy-duty vehicle transport on its highway systems. This growth has had substantial impacts on roadway deterioration, urban and suburban traffic congestion, and particulate and ozone air quality problems. Recently, National Ambient Air Quality Standards (NAAQS) for particulate matter and ozone have been revised to a more stringent level. State and metropolitan area planners and decision makers will be required to more aggressively implement strategies to reduce ozone and particulates associated with all components of the transportation system. A major contribution to this pollutant reduction will have to come from heavy-duty vehicles and their operations. However, accurately tracking and monitoring heavy-duty vehicle emissions, specifically oxides of nitrogen (NOx), volatile organic compounds (VOCs), both contributors to the ozone problem, and particulate matter (PM), is extremely difficult compared with other types of vehicles.

Travel patterns of heavy-duty vehicles in urban areas are irregular and difficult to track and model. Without understanding their travel patterns and emission rates, there is no basis for determining cost-effective strategies to reduce negative air quality impacts from heavy-duty vehicles. Without such understanding, state departments of transportation (DOTs), MPOs, and other agencies cannot fully evaluate policy options, planning initiatives, or programming commitments, especially in terms of achieving air quality objectives. Finally, for multimodal solutions to meet the needs of urban regions and states, heavy-duty vehicle impacts must be fully and accurately integrated into transportation and air quality planning.

Objective: The objectives of this research are as follows: (1) enhance the basic understanding of heavy-duty vehicle activities and associated emissions; (2) develop tools for MPOs and states to evaluate future policies, plans, or programs on exhaust emissions (including NOx, PM, and VOCs); and (3) test, evaluate, and apply the tools in order to demonstrate their applicability to the transportation and air-quality planning processes.

Tasks: Phase I--Heavy-Duty Vehicle Usage Patterns: (1) Identify and evaluate existing data sources and synthesize current research and planning activities associated with heavy-duty vehicle usage patterns. (2) Develop and characterize heavy-duty vehicle operating factors based upon heavy-duty vehicle classes, usage patterns, and operating conditions for various area types (e.g. urban area, suburban, regional, and interstate). Also include a range of roadway types within the given areas. (3) Prepare an interim report that summarizes the findings of Phase I and identifies the need for specific data improvements.

Phase II--Heavy-Duty Vehicle Emission Factors and Rates: (4) Identify and evaluate existing data sources and synthesize current research and planning activities associated with heavy-duty vehicle emissions. (5) Develop and estimate emission factors for NOx, PM-2.5 (particulates with a diameter of less than 2.5 micrometers), and VOCs by the vehicle classes, usage patterns, and operating conditions developed in Task 2. It is expected that these estimates would be based on existing data sources. Compare the estimates to emission factors from current versions of the MOBILE, PART, and EMFAC models. (6) Prepare an interim report covering Phase II that identifies the need for specific data improvements. Discuss the information in the Phase I and II interim reports at a meeting of the panel and obtain NCHRP approval before initiating Phase III.

Phase III--Development of Analytic Tools and Application Methodology: (7) Analyze and integrate the emissions factors developed in Task 4 and the operating factors developed in Task 2. (8) Develop and document an analytic tool (or tools) that can support the development and evaluation of policy, plans, and programs related to heavy-duty vehicle operations and emissions. (9) Develop, test, and refine an application methodology for employing the analytic tool(s) developed in Task 8. Ensure compatibility with current transportation planning tools. (10) Prepare a plan for identifying and selecting cases for the application of the methodology and tools developed in Tasks 8 and 9. Include the justification for the case locations, geographic considerations, data availability, staff capabilities, and other selection factors. Obtain panel approval prior to initiating Task 11.

Phase IV--Application and Evaluation of Analytic Tools and Application Methodology: (11) Apply the analytic tool(s) and methodology to at least one metropolitan area and to one state. Assess strengths and weaknesses in terms of supporting policy analyses, transportation planning, and priority programming. Present the applications in the form of case studies. (12) Refine and revise the methodology and tool(s) as needed based upon the application assessment in Task 11. (13) Prepare a plan for maintenance, distribution, and support for the analytic tool(s) and the application methodology. (14) Prepare a final report that documents the entire research effort and includes the case studies applications. Also include the needs and opportunities for improved data identified in Phases I and II and the maintenance plan developed in Task 13.

Status: The research is completed.

Product Availability: The agency final report is available for a limited time on a loan basis from NCHRP.