Comparison of MOBILE4.1 and MOBILE5 predictions with measurements of vehicle emission factors in Fort McHenry and Tuscarora mountain tunnels

Measurements of motor vehicle emissions at Tuscarora Tunnel in Pennsylvania and Fort McHenry Tunnel in Maryland were compared with predictions of the U.S. Environmental Protection Agency (USEPA) mobile-source emission models MOBILE4.1 and MOBILE5. Both models usually agreed to within ± 50% with the observed emission rates, with MOBILES consistently predicting higher emission factors than MOBILE4.1. At Tuscarora, which is level, both models tended to overpredict. At Fort McHenry, which has grades, MOBILE4.1 underpredicted, and MOBILE5 overpredicted.