Evaluation of Level-of-Service Measures for Two-Lane Highways with a Simulation Model

Most highway capacity guidelines use two main traffic measures to establish the level of service for two-lane highways: average travel speed (ATS) and percentage of time spent following (PTSF). In the Highway Capacity Manual (HCM), directional ATS is related to volume by using a linear expression with a single coefficient for volume in both directions (travel and opposing), whereas in other capacity guides such as those in Germany, Finland, and Brazil, a nonlinear form of expression is used; some of these expressions use different coefficients for travel and opposing volumes. In the HCM, directional PTSF is related to volume by using an exponential expression. Other models use a slightly different exponential form of model with different coefficients. The purpose of this research is to use a newly developed and calibrated two-lane microsimulation model to investigate the relationship between traffic volume and directional ATS and PTSF. New expressions are suggested and subsequently compared with those of ...