Toward an Improved Understanding of Vehicle Emissions
The importance of understanding and accurately quantifying the amount of pollutants discharged from vehicles using urban roads continues to increase. Currently it is common practice to estimate of the quantity of pollutants discharged from individual vehicles and entire fleets, by using emission models (e.g. USEPA Mobile6). Recent studies show that vehicle emission models often do not provide accurate estimates of real-world emissions. This paper explores three issues which are important to and if resolved will lead toward improved estimates of vehicle emission factors.
A large set of tailpipe emission data has been collected from on-road vehicles using remote sensing technology. Eight vehicles have been put through the IM240 cycle on a dynometer and their emissions measured using the same technology. The on-road and dynometer data have been used to generate two sets of emission factors. The on-road, real world emission factors are compared to those produced by the more traditional IM240 test cycle.
The question of whether or not vehicle fleet emissions vary from region to region is explored via a case study. The case study employs and compares on-road vehicle emission data from two distant cities within New Zealand.
The issue of non-tail pipe PM10 emissions from roadways is considered. The results of a roadside monitoring campaign are presented and used demonstrate the influence of non-tailpipe PM10 discharged from a near by road. A first pass estimate of the amount of non-tailpipe PM10 discharged from vehicles is made.