This paper describes the new facilities in the recently released Version 4 of the SCOOT urban area traffic control program. The new feature expected to interest traffic managers most is the on-line estimation of vehicle emissions of pollutants. These estimates are based on a mathematical model commissioned by the UK Department of the Environment, Transport and the Regions (DETR); the ASTRID database can store these estimates and allow the analysis of historical patterns of emissions. The chosen model is based on the following data: (1) the traffic flow on each link; (2) the mean speed on each link, averaged over all vehicles; (3) the proportions of four classes of vehicles on each link; and (4) distance travelled. Emissions of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOC), and particulates (PM) are estimated, using emission-rate data in the form of a set of functions linking vehicle speed to emission rate. For each vehicle class and pollutant, the emission function is a given polynomial function of speed. Several enhancements have been made to SCOOT's cycle time optimiser, to increase its responsiveness to traffic conditions and to traffic managers' commands. New logic enables the use of information from existing stopline loop detectors.
Abstract