This article describes efforts by the Texas Transportation Institute (TTI) to apply the Environmental Protection Agency's MOBILE emissions rating program to estimate on-road mobile source emissions in Texas. Under the Clean Air Act, the government sets limits for "criteria pollutants," which are ozone, particulate matter, carbon monoxide, lead, nitrogen dioxide and sulphur dioxide. In Texas, the primary pollutants of concern are nitrogen oxide, carbon monoxide and volatile organic compounds. Researchers at TTI have developed procedures that estimate emissions for vehicles on the road, using MOBILE, which models for 28 vehicle types, operating on four roadway types and under a range of conditions. This permits an extremely detailed analysis of emissions, including an activity measure like vehicle miles travelled and speed for every hour of the day, on every link of the roadway network, and by road type for each of the 28 vehicle types. Included is a chart with primary air pollutants and some detail about key activity measures.
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