Lambert W Function Based Semi-Analytical Framework for Estimation of Speed and Passenger Car Unit

Abstract

Developing speed model is challenging particularly when vehicles with diverse static and dynamic characteristics use the same carriageway without any segregation. The traffic composition in this case, plays an important role in determining the speed. Determination of Passenger Car Unit (PCU) requires speed information of individual vehicle types. On this background, the present work aims to study the influences of traffic volume and its composition on speed and PCU of individual vehicle categories. Classified traffic volume and speed data were collected from several mid-block locations on two lane undivided urban roads. While formulating the speed model, Lambert W function was purposefully incorporated. Validation results showed a good agreement between the observed speeds and the speeds predicted by the model developed. The predicted speeds by the model were utilized in estimation of PCU. Finally, the sensitivity analysis was performed to capture the influence of traffic volume on individual speed and PCU.