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Carbon Monoxide Impacts of Automatic Vehicle Tolling Operations


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Suggested Citation:
Washington, Simon P. and Randall L. Guensler (1995) Carbon Monoxide Impacts of Automatic Vehicle Tolling Operations. Institute of Transportation Studies, University of California, Davis, Presentation Series UCD-ITS-RP-95-18

Proceedings of the National Conference on Intelligent Transportation Systems and the Environment

Intelligent transportation technologies (ITTs) are being promoted as a means of reducing congestion delay, improving transportation safety, and also as a means of making vehicle travel "...more energy efficient and environmentally benign." In theory, IVHS technologies will increase the efficiency and capacity of the existing highway and roadway systems to reduce congestion. We are not confident, however, that vehicular emissions will be reduced by the full range of proposed ITTs.

The transportation-air quality community has lacked the appropriate tools in which to predict the effects of microscopic changes to vehicular activity induced by ITTs. The currently used emissions models, EMFAC in California, and MOBILE in the remainder of the US, are unable to provide the resolution needed to quantify the effects of these changes. Research at UC Davis is focusing on estimation ofa statistical 'modal' model capable of simulating the emissions impacts from individual vehicles under various operating scenarios. The emissions model, currently a significantly modified version of the mathematical algorithms employed in the CALINE 4 Line Source Dispersion Model developed by Paul Benson and others at Caltrans, predicts carbon monoxide (CO) emissions based upon individual vehicle speed-time profiles and laboratory measured emission rates. The model, therefore, can be used to quantify vehicular carbon monoxide emissions under various ITT scenarios.

This paper examines the carbon monoxide (CO) emission impacts of one such applied ITT, namely Automatic Vehicle Identification (AVI) used to implement electronic tolling. AVI used in place of conventional toll booths has previously been identified as an ITT that is likely to offer air quality benefits. By allowing vehicles to be tolled either through a windshield displayed debit card, or by some other mechanism, vehicles could forgo the deceleration, stop-delay, and ensuing acceleration that results from an encounter with a conventional toll plaza. The results presented here represent the beginning stages of an ongoing emissions modeling effort. Future work will incorporate an improved model for CO, and models for hydro-carbons and oxides of nitrogen.