Estimation of PCU and Saturation Flow at Signalised Intersection

Abstract

In homogeneous form of traffic, the vehicles in traffic are not so versatile and the vehicles move in dedicated lanes, whereas in countries such as India, the form of traffic is heterogeneous in nature where the traffic is very versatile with many combinations of vehicles which rarely move in dedicated lanes. The combinations make it harder to calculate the headway, PCU, etc. because every vehicle possesses a different shape and size. The lack of use of dedicated lanes makes it very tough to check which vehicle belongs to which queue and how it will move or accelerate. Hence, the methodology used for homogeneous traffic condition fails drastically when used in heterogeneous traffic conditions. The recent researches based on heterogeneous form of traffic do not present us with a reliable methodology to compute or calculate the saturation flow in heterogeneous traffic condition. This makes it difficult to design and plan the working of intersections because the traffic almost always tends to move differently than the calculated outcome. The current research is primarily focused on the development of a reliable methodology which can present us with a more accurate saturation flow traffic data, i.e. intersection capacity in heterogeneous traffic conditions. In the clearance method, different factors such as effective turning radius, projected area of the vehicles, etc. are required for the calculation of saturation flow. In velocity method, during a traffic jam all the vehicles are almost at the same speed so the PCU deviates from its actual value making all PCU values of different vehicles almost the same. In India, we have heterogeneous type of conditions not homogeneous and also the lane discipline is not followed. In this clearance method, the study considers only a particular type of vehicle at an instance and we have to determine the clearance time it requires, i.e. the time it takes from curb line to front curb line.