Evaluation of level of service for two-lane roads in Sri Lanka

Abstract

Two-lane roads form a major part of Sri Lanka‟s road network. The ability to accurately estimate lane capacity and Level of Service (LOS) is a key element in highway planning and manage-ment, which is essential to develop an efficient road network. The current methodologies to estimate capacity and level of service do not satisfactorily incorporate the traffic and roadway characteristics in Sri Lanka. Speed-density models were developed using traffic flow data from surveys carried out at 14 locations, where the speed, flow, vehicle type was recorded. In addition, PCU factors were derived for eight vehicle types. The speed-flow model was derived from the results to calculate the capacity for a two-lane road, which was also adopted to define new threshold values for parameters such as average travel speed, volume to capacity ratio to evaluate LOS. The capacity estimate and new LOS evaluation criteria offers more applicable parameters to assess the existing highway condition for highway upgrading and it can be incorporated into transport planning models as an input when de-fining road network parameters.