| Two vehicle emission models, MOBILE and EMFAC, are currently mandated for air quality analysis by the U.S. Environmental Protection Agency (EPA) and the California Air Resources Board (CARB), respectively. A major shortcoming with the models is the non-inclusion of roadway geometric characteristics, particularly the road grade, in the model algorithms. Road grade is important for two main reasons: its effect on vehicle activity, and its impact on vehicle emission rates. In the continuing revisions of the models both the EPA and CARB have not yet included a road grade correction factor. One reason for this is the current lack of a cost-effective method to map the grade on millions of miles of roads in the country.; This research addressed this problem by developing a cost-effective methodology to measure roadway grade in kinematic mode. Specifically, a hardware system comprising a fiber-optic gyroscope, a global positioning system (GPS) receiver, and a data-logging computer was designed. The components were integrated with appropriate software programs such that when mounted in a moving vehicle the gyroscope output measures the roadway grade and the GPS receiver output gives the spatial (latitude, longitude) location associated with each grade value. The spatial resolution of the grade data is sufficiently small for the data to be employed in the emerging GIS-based vehicle emission models for project-level air quality analysis. |
