Emissions testing will be performed while the vehicle is operating over a simulated transit duty cycle. This cycle will consist of a modified Advanced Design Bus operating cycle. Sampling equipment will be used to extract gas and particulate samples for analysis. Analysis instrumentation will be used to detect and measure the levels of CO, CO2, NOx, and HC. The results of this test may be used by transit operators for making relative comparisons between buses.

Emissions testing for Environment Protection Agency (EPA) compliance certification is typically conducted on a new engine in a test cell. While standardized procedures and test cycles have been developed by the EPA for this type of compliance testing, no standardized test procedures or cycles exist for testing an in-vehicle engine operating on a simulated transit duty cycle. The chassis dynamometer test will be performed on a engine after the bus has accumulated several thousand miles of operation, thus providing a more realistic indication of the level of emissions that can be expected in actual transit service. Detailed test procedures will standardize testing for each bus category, including alternative fueled vehicles, to be tested. This testing will provide a relative comparison of the levels of emissions produced for each bus