Mining Vehicle Probe Data to Establish Vehicle Activity Distributions on the National Highway System
Under 1 year
Research Idea Scope
The use of mobile source emissions models is inescapable for many regulatory, planning, and research applications in the air quality and transportation field. Although the U.S. Environmental Protection Agency’s MOVES model and the California Environmental Protection Agency’s EMFAC model are distributed with default databases, the latest local information available is most appropriate to use for improving the accuracy, reliability, and representativeness of model estimates. An evaluation of State submissions to the National Emissions Inventory by the Coordinating Research Council, Inc., found that local average speed distribution data required by the MOVES model are challenging to obtain, particularly for rural areas and urban areas not employing travel demand models. The Federal Highway Administration (FHWA) maintains the National Performance Management Research Data Set (NPMRDS) of vehicle probe data consisting of actual, observed measurements of average travel times for the entire National Highway System. The data are collected every 5 minutes, 24 hours a day, 7 days a week. For each 5 minute bin, 3 distinct travel times are provided – for passenger traffic, freight traffic, and all traffic combined. Each 5 minute bin also includes temporal and spatial elements of date, time, state, county, latitude, longitude, road number, road name, functional class, direction of travel, and segment distance. The data are up-to-date, reported mid-month for the previous month, beginning in July 2013. FHWA may authorize access to the data to any agency that is a State Department of Transportation or Metropolitan Planning Organization receiving federal transportation funds. Authorized agencies may grant contractors the right to use the data for approved purposes. Agencies may not sell, share, or otherwise transfer vehicle probe data to other public entities or private entities for unapproved purposes. The proposed research consists of two phases. The scope of Phase 1 is to evaluate the utility of the NPMRDS vehicle probe data to develop vehicle activity distributions in lieu of default distributions for use in mobile source emissions analysis. The research will ascertain all potential uses of the data for emissions analysis, in addition to the most obvious use of developing average speed distributions. The research will also recommend the circumstances best suited for applying NPMRDS-based vehicle activity data, such as inclusion in the default databases distributed with the regulatory mobile source emissions models; state submissions to the National Emissions Inventory; constructing state and national emissions inventories; transportation planning for rural and urban areas not employing travel demand models; and project development tasks requiring current data. The research will also identify any representativeness issues inherent in the data set with respect to sampling error, accuracy, and precision. The scope of Phase 2 is to develop the methodologies, procedures, and tools needed to utilize the NPMRDS vehicle probe data to create the vehicle activity distributions identified in Phase 1. For example, determine actual vehicle speeds based on available measurements of average travel times and distances for direct use in the emissions models. The research will include a demonstration of how its purpose is fulfilled with practical applications of creating vehicle activity distributions for use in regional and project-level emissions modeling.
Urgency and Payoff
The availability of up-to-date vehicle activity, such as average vehicle speeds, on an extensive highway network based on actual, observed measurements is virtually non-existent. The promise of the FHWA National Performance Management Research Data Set is to provide such information with additional beneficial details for mobile source emissions modeling, such as hour-by-hour variability 24 hours a day, 7 days a week; for trucks and non-trucks; by direction of travel; and by road type. The payoff is enhancing vehicle activity inputs to emissions models toward improving the accuracy, reliability, and representativeness of model estimates.
Michael Claggett U.S. Dept. of Transportation, Federal Highway Administration (505) 820-2047