Complete Enough for Complete Streets? Sensitivity Testing of Multimodal Level of Service in the Highway Capacity Manual

An increasing number of jurisdictions across the United States are exploring level of service (LOS) for multiple travel modes, in part as a result of the release of the Highway Capacity Manual 2010 (HCM 2010), as well as an increased focus on complete streets policies. One of the most important questions being asked by these jurisdictions is whether new multimodal LOS methods are sensitive enough to inform transportation investments, mitigate impacts, and prioritize future projects. For this paper, transportation professionals (public, private, and academic) were surveyed about the inputs believed to have the greatest effect on pedestrian, bicycle, transit, and auto LOS or the inputs thought to have the greatest likelihood of being changed (e.g., to mitigate an impact or to improve existing conditions). Sensitivity testing was then performed at locations in four cities to measure how the HCM 2010 multimodal LOS scores responded as these inputs were incrementally increased or decreased. Although many inputs performed as expected, the testing also found model responses that were of a questionable direction or magnitude. The results of this study are informative for agencies that are considering adopting the HCM 2010 multimodal LOS for mitigation, resource allocation, and strategic decision making. The results also provide a starting point for additional research needed to enhance multimodal LOS methods.