Impact of stops on vehicle fuel consumption and emissions

Macroscopic emission models use average speed as a sole traffic-related explanatory variable. Research, however, has demonstrated that the use of average speed as a single traffic-related explanatory variable is insufficient in estimating vehicle emissions. The objective of this paper is to attempt to quantify, using simple examples, the impact of vehicle stops on fuel consumption and emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen. This study indicates that the vehicle fuel consumption rate is more sensitive to cruise speed levels than to vehicle stops. The aggressiveness of a vehicle stop, as represented by the vehicle's acceleration and deceleration level, does have a significant impact on vehicle emission rates. Specifically, HC and CO emission rates are highly sensitive to the level of acceleration when compared to cruise speeds in the range of 10 to 120 km/h. Alternatively, the impact of deceleration levels on all measures of effectiveness is relatively small. Noteworthy is the fact that at high speeds the introduction of vehicle stops involving extremely mild deceleration and acceleration levels can actually reduce vehicle emission rates