The effects of transportation system characteristics on the success of congestion mitigation strategies for reducing traffic congestion and air pollution

Date of Completion

January 1999


Engineering, Civil|Engineering, Electronics and Electrical|Engineering, System Science




The research develops a heuristic transportation-air quality study especially designed to achieve understanding of how congestion mitigation strategies applied to different types of land use developments, defined by transportation system characteristics, affect the improvement of emission-related air quality in the area. Land use developments are defined by four transportation system characteristics: land use type, land use density, traffic signal density, and through traffic volumes. ^ This study examines four types of congestion mitigation strategies commonly encountered in transportation planning practice: (a) CMS 1—adding one left turn lane at signalized intersections with protective left turn phase; (b) CMS 2—same as (a) with permissive left turn phase; (c) CMS 3—adding one lane each direction and one left turn lane at every intersection with protective left turn phase, and (d) CMS 4—same as (c) with permissive left turn phase. ^ The study performs a microscopic analysis of the impacts of individual strategies on congestion and air quality. The analysis is carried out using a series of programs, including some written specifically for this work to perform land use simulation, trip generation, and trip distribution, and off shelf software, such as PASSER IV-94 and TRAF-NETSIM for traffic simulation, MOBILE5a_h for emissions estimate, and SPSS Base Release 7.5 for statistical analysis. ^ These strategies are studied in the context of different types of land use, development density, and traffic control to see how these variations affect the resulting air quality and traffic operations. Two types of measures of effectiveness, average travel time and emission inventories of CO, HC, and NOx pollutants, will be used in this study to represent congestion and air pollution measures, respectively. ^ The findings indicate that each transportation system characteristic has significant effects in reducing congestion and air pollution. The CMS 4 is the best alternative for most cases and permissive left turn phasing is better than protective phasing for majority of the cases. ^