Of course, nobody can predict the future with absolute certainty. But we can model what the future will probably look like, given a set of conditions. Modeling provides a cost-effective way to estimate the impact of proposed actions under various assumptions.
The Transportation Modeling Program develops accurate, reliable methods and procedures for estimating mobile source emissions. We specialize in forecasting on-road mobile source emissions to demonstrate compliance with planning and air quality regulations.
Armed with these emissions forecasts, sponsors can show how they’re meeting the goals outlined in the state implementation plan. Once an area has exceeded the standard, it must “demonstrate conformity”—the area must prove how it will achieve the standard and how future emissions will not exceed allowed levels and throw it back into non-attainment. Our work gives them exactly that information.
Researchers in the Transportation Modeling Program estimate emissions for vehicles using EPA‘s emissions rate program called MOVES. Our approach enables the application of MOVES routines at an extremely detailed level. We rely on three key activity measures for our estimates of an area’s compliance:
- Vehicle miles traveled (VMT) – Generally speaking, the more VMT you have, the more emissions you have. VMT is estimated by year, seasonal day type (e.g., summer weekday), hour of the day and direction (peak or off-peak), for each roadway type (e.g., freeway, arterial, collector, etc.).
- Speed – Speed is a function of the ratio of roadway volume to capacity and is estimated for each link (roadway segment) in the transportation system.
- Vehicle type – Emissions rates for 28 different types of vehicles (categorized by fuel type and gross vehicle weight rating) are produced. The mix of these 28 types is estimated by roadway type and time of day.
MOVES allows us to incorporate each of these three measures under various current and future conditions to predict an area’s emissions. It’s this information the sponsor then uses to demonstrate projected compliance with air quality standards, or develop appropriate emissions reduction strategies.