Rural Freeway Level of Service Based on Traveler Perception

Abstract

The concept of level of service (LOS) is meant to reflect the trip quality a traveler will experience on a roadway or other transportation facility. The objective of this study is to provide insight into how road users perceive trip quality on rural freeways and to examine how the existing service measure (density) relates to the perceived trip quality. Study participants were shown a series of video clips of rural freeway travel from a driver's perspective. They then filled out survey forms indicating their opinion of the trip quality provided by the conditions in the video clip. The survey participants were also asked to give background information about themselves and their driving habits. The data from the surveys were analyzed on the basis of an ordered probit model. The first model used only density as a predictive factor. The second took other roadway and traffic characteristics into account, and the third examined all the significant factors obtained from the survey. The “density only” model confirmed that density is a strong indicator of travelers’ perceptions of trip quality. The other models showed the significance of other traffic and roadway factors in the perception of trip quality, as well as some socio-economic information and personal driving habits. A set of LOS thresholds was also calculated for the “density only” model on the basis of the survey participants’ responses. The resulting thresholds were considerably lower than the Highway Capacity Manual (HCM) thresholds for all LOS rankings. This suggests that travelers’ tolerance of congestion is lower on rural freeways than the HCM indicates.