Estimating passing sight distances for overtaking truck platoons – Calibration and validation using VISSIM

Abstract

Two-lane highways comprise a substantial proportion of the nation’s highways. One of their critical aspects is the passing sight distance (PSD), which is the minimum distance required for executing a safe passing maneuver using the opposing travel lane. Sight distances that are shorter than the available PSD warrant the designation of no-passing zones. The PSDs, documented in the Manual on Uniform Traffic Control Devices, are developed based on the premise that only one slower moving impeding vehicle is being overtaken. Yet, the oil and gas industry in Wyoming advises its truck drivers to travel in platoons creating a complicated situation for trailing vehicles. Passing a single impeding vehicle is cumbersome, not to mention passing multiple trucks. The PSD is augmented by the length of each truck in the platoon and the spacing among the trucks. In this research, an existing mathematical kinematics PSD model is implemented to compute the PSDs needed to pass multiple oil and gas trucks for a variety of scenarios belonging to two-lane highway segments with posted speed limits of 70 mph. The PSDs computed range from 1385 to 1915 ft depending on the number of trucks in the platoon and spacings between the trucks. The results are compared with those of VISSIM microsimulation models, which are validated using field traffic volume data. The discrepancies between the computed PSD results and those of the simulations are less than 3%. Furthermore, it is recommended to deploy passing lanes to mitigate the effects of truck platoons on traffic operations.