Quality of Service on freeways: Are we talking the same language?

The perception of driving conditions by motorists and passengers should be the basis for assessing Quality of Service (QOS) on highway facilities. This perception has been an essential part of the QOS concept since it was first introduced by the U. S. Highway Capacity Manual (HCM) in 1965. However, none of the HCM QOS freeway procedures to date has accounted for this perception. This paper describes the early stages of ongoing research at McMaster University to investigate drivers' perception of the QOS on freeways. The paper includes a discussion of some important issues that are thought to affect drivers' perception of the QOS on freeways. These issues are namely; scale of analysis, range of traffic operations, trip purpose, facility type, drivers' past experience, and the indicators of drivers' perception of the QOS. For each of these issues, hypotheses were made on drivers' perception that, if verified by the research, will have important implications for future improvements to the QOS procedures.