| Planners and decision-makers use transportation and emission models to determine local conformity with air quality regulations. For heavy-duty vehicles, emission rates are highly correlated with engine load, which in turn is a function of vehicle weight, road grade, and onroad vehicle operations. Load-based emission models are currently being developed by the USEPA and other universities at the national level for various classes of heavy-duty vehicle engine technology. However, current onroad data for engine technology class and heavy-duty vehicle weights are inadequate to link with these new models (due to non-representative samples included in truck surveys and the predominance of non-urban weigh-in-motion sites). Therefore, the heavy-duty portion of emission models requires new input data to properly integrate with current transportation models.; The goal of this research is to develop a procedure for collecting heavy-duty vehicle weight and horsepower data and to develop models that will predict the percentage of activity for various temporal and spatial conditions in a metropolitan area. Portable weigh-in-motion equipment, State of Georgia weigh station data, and roadside truck surveys are used to collect data for the onroad heavy-duty vehicle fleet. This research statistically measures the interaction between heavy-duty vehicle class, weight and horsepower distributions. The application of these results will improve heavy-duty emission models by allowing for temporally and spatially disaggregated heavy-duty vehicle data inputs to generate more accurate emissions estimates. |
