Heavy vehicles emit emissions at different rates than passenger vehicles. They may behave differently on the road as well, yet they are often treated similarly to passenger vehicles in emissions modeling. Although not frequently considered in calculating emission rates, differences in the operating speeds of passenger vehicles and heavy trucks may influence emissions. The main goal of this research project was to evaluate whether heavy trucks typically travel at significantly different operating speeds than passenger vehicles and what impact differences in on-road speeds would have on emissions. Average speeds and spot speeds were collected for heavy trucks and passenger vehicles for four arterial segments and spot speeds were collected for two freeway segments in Des Moines, Iowa. Average and spot speeds were collected for four arterial segments and three freeway segments in the Minneapolis/St. Paul, Minnesota metropolitan area. The results of this research show that heavy trucks and passenger vehicles operate differently on the road. Average and spot speeds were compared for heavy trucks and passenger vehicles by facility. Average and spot speeds for heavy-duty trucks were lower than for passenger vehicles for all locations. Differences could have consequences for project level and regional emissions modeling particularly since the ability to demonstrate conformity is based on the ability to correctly estimate and model vehicle activity. (Author/publisher)
Abstract