3. Study of the Effect of Stream Mix on Saturation Flow Rate of Heterogeneous Traffic Using Computer Simulation
Date of Start

May 2005
Indian Institute of Technology Madras (R, C)


Scope and Objectives

(i) To study the saturation flow characteristics of heterogeneous traffic with mixed streams at signalized intersections using field observed data.

(ii) To modify the available computer program package to simulate heterogeneous traffic flow to suit the requirements of the present study and calibrate the modified model.

(iii) To validate the model using field observed traffic data.

(iv) To apply the validated model to study the saturation flow of heterogeneous traffic with various roadway and traffic conditions to obtain guideline values of saturation flow of heterogeneous traffic with stream mix.

The project work aims at study of stream mix in the saturation flow rate of heterogeneous traffic at signalized intersection. (i) As the first step of the study a set of approaches to signalized intersections carrying mixed traffic stream (mix of straight on and turning streams) is identified.

(ii) Then the geometric details of the approaches along with the general intersection details are collected.

(iii) The traffic flows on the selected approaches are then measured by making a classified count of vehicles, when the vehicles cross the stop line during the saturated green time.

(iv) The available model of traffic flow through signalized intersection is modified to suit the requirements of this study.

(v) The modified model is then calibrated using the field observed traffic data to enable application of the model for a wide range of road geometry and traffic volume and composition.

(vi) The model is then applied to measure saturation flow rate for various roadways and traffic situations to finally arrive at a set of guideline values of saturation flow, which will serve as an important input for optimal design of traffic signals.
Findings and Conclusions
It was found that the value of saturation flow is relatively maximum for the combination of straight going and right turning streams, and minimum in the case of the combination of straight going, left turning and right turning streams, while the value for the combination of straight going and left turning streams lies in between the two. Also, it has been found that there is no common trend in variation of the saturation flow due to variation in traffic compositions.