Highway Research Record

Heterogeneous Traffic Flow Modelling using Cellular Automata

Date of Start:August 2003
Indian Institute of Technology, Delhi (R)

(i) Collecting data on vehicle counts, speeds and road occupancy, which are not having any ambiguity, over a homogeneous     two-lane road.
(ii) Understanding the traffic stream nature, with the help of proposed traffic stream characteristics and their relationship with      each other under varying traffic conditions.
(iii) Extending the features of CA traffic flow model to make it suitable for modelling heterogeneous traffic with no lane      discipline
(iv) Simulating and validating the traffic flow models at microscopic level under varying traffic conditions over a mid-block section      of a homogeneous road

The methodology is discussed in two parts, first one regarding data collection and second for modelling. Since no comprehensive studies were carried out in understanding the empirical features of heterogeneous traffic emphasis is given to collect extensive traffic data on National Highways.

(i) As this study involves understanding the empirical feature of heterogeneous traffic, data has been collected over a mid      block road section (near both ends of the mid-block) and it is also planned to collect data near an upstream section of an      intersection to get the empirical traffic features in free and congested traffic conditions
(ii) Traffic stream characteristics such as flow, in absolute number of vehicles, average speeds of different classes of vehicle      were obtained from the field measurements.
(iii) Extensive analyses are planned to understand the nature of heterogeneous traffic, e.g., how the vehicles are entering into      platoons, vehicle behaviour in platoons and dispersal patterns of platoons.

From modelling point of view, the basic hypothesis behind the methodology is that “no lane discipline of traffic in developing countries arises due to the wide variations in vehicle dimensions as well as in the mechanical characteristics”. Since the space is available for passing and over taking two wheelers and three wheelers would try to utilize the space and avoid following. Based on the above said reasons, it can be said that heterogeneous traffic is utilizing the road space more effectively than homogeneous traffic. This is the nature that leads to the distribution of vehicles in lateral direction. Keeping in view of the above said traffic characteristics, it is planned to develop a suitable model for heterogeneous traffic.

Ch. Mallikarjuna and K. Ramachandra Rao, (2005) “Traffic Flow Modelling on Highways using Cellular Automata: A Review”’ Proceedings of International Conference on ‘Structural and Transportation Engineering (START- 2005), N.Delhi, pp 912-919.