Microscopic Modeling of Vehicle Start Emissions

A microscopic framework for estimating instantaneous vehicle start emissions for light-duty vehicles and trucks is developed. The framework assumes a linear decay in instantaneous start emissions over a 200-s time horizon. The initial vehicle start emissions rate is computed by using the soak time function of the U.S. Environmental Protection Agency’s MOBILE6 model, assuming a 200-s decay time interval. The use of the MOBILE6 soak time function ensures that the microscopic procedures that are developed produce start emissions that are consistent with the MOBILE6 model. The validity of the framework was demonstrated using independent trips that involved cold-start and hot-start impacts with vehicle emissions estimated to within 10% of the test in-laboratory measurements.