The mode of heavy trucks has traditionally not received specific attention as far as level of service is considered.  Trucks are typically converted to an “equivalent” number of passenger cars and the Highway Capacity Manual (HCM) LOS analysis procedures determine a single LOS measure for the traffic stream as a whole, without distinction of possible LOS differences between the different modes operating in that stream.

This project consisted of an exploratory investigation, and development, of a methodology for assessing the level of service of heavy trucks in the traffic stream separately from that of passenger vehicles, for basic freeway segments.  This methodology is based on a ‘relative maneuverability’ concept, which is a function of the ratio of percentage of free-flow speed of trucks to percentage of free-flow speed of passenger cars.  Speed prediction equations were developed for various classes of trucks, as well as for the passenger car, for use in calculating a ‘Relative Maneuverability Index’, which is subsequently used to determine truck level of service.  Microscopic simulation was used for the speed prediction model development.