Freeway Systems Research Beyond Highway Capacity Manual 2000

The Highway Capacity Manual 2000 (HCM 2000) contains new procedures for the analysis of directional freeway facilities that were developed and assessed during the past 3 years by a research team. This experience in developing the freeway facility chapter and, later, in assessing these procedures has led to the identification of freeway research needs beyond HCM 2000. The findings of the assessment process for HCM 2000 procedures and other traffic models are highlighted, and recommendations for future research are provided. Areas of investigation and identified research needs include free-flow speed estimation, upper-limb speed-flow relationships, capacity estimation, lower-limb speed-flow relationships, characterization of the oversaturated regime for freeway facilities, and other traffic models.