Saturation Flow Model at Signalized Intersection for Non-lane Based Traffic

The important parameters in the planning, design and control of a signalized intersection are saturation flows, lost times and passenger car units (PCU). These factors have been traditionally measured, in most western countries, based on the research carried on test tracks and on public roads where traffic is typically car-dominated with vehicles moving in clearly defined lanes. However, the traffic movement in Bangladesh and in other developing countries is rendered in more complex due to the heterogeneous characteristics of the traffic stream using the same right of way. Another striking feature of the road traffic operating condition in developing countries is that, despite having lane markings, most of the times lane discipline is not followed no matter whether non motorized vehicle is present or not. At intersection, there is notable lateral movement and vehicles tend to use lateral gaps to reach the head of the queue. Due to fundamental differences in traffic characteristics, the standard western relationships for predicting the values of saturation flows, lost time, and PCU factors are not appropriate for developing countries. This paper first review principle methods of measurement of saturation flow and selection of proper method to measure this parameter for the traffic condition prevailing in developing countries. The research establishes that unified PCU concept is not true for non-lane based traffic condition. It also proposes PCU and a flow model for estimating capacity of signalized intersection having no lane discipline