Performance Measures for Truck Level of Service

The current Highway Capacity Manual (HCM) provides analytical methods to evaluate performance levels of transportation facilities and to estimate level of service (LOS) perceived by the users. The HCM methodologies yield a single LOS value for all users in a traffic stream. However, because of the unique size and operating characteristics of large trucks, truck mode users may perceive LOS on various roadway facilities on the basis of different criteria than those of other mode users. A study was conducted to determine, from an LOS perspective, what roadway, traffic, and control issues should be focused on to better serve the needs of the trucking community. This paper describes the second part of the study, in which a survey of truck drivers and truck company managers was performed to quantitatively measure the relative importance, satisfaction, and improvement priority of truck LOS determinants and to examine which aspects of a truck trip should be analyzed to estimate truck LOS on each roadway type. Speed variance and pavement quality were identified as the service measures for truck LOS on freeways, while percent time being followed, percent time spent following, and travel lane and shoulder width and their pavement quality were identified for truck LOS on two-lane highways. Truck trip quality on urban arterials was found to depend on factors such as ease of turning maneuver, speed variance, traffic density, and pavement quality. Other drivers’ behavior, pavement condition, level of congestion, and frequency and timing of construction activities were common major contributors to truck LOS regardless of roadway type.