The composition of traffic in developing countries is mixed, with a variety of vehicles, motorized and nonmotorized, using the same right-of-way. The motorized or fast-moving vehicles include passenger cars, buses, trucks, auto-rickshaws, scooters, and motorcycles; nonmotorized or slow-moving vehicles include bicycles, cycle-rickshaws, and animal-drawn carts. The proportion of slow-moving vehicles in the traffic stream may vary from 10 to 80 percent. Since the 1950s, considerable research has been done to develop traffic flow models for roadways with mainly motorized vehicles or homogenous traffic, representing the composition of traffic primarily in industrialized countries. A review of the literature has shown that limited studies have been done to develop an understanding of traffic flow for non-lane-based heterogeneous or mixed traffic conditions in developing countries. Some efforts have applied a variation of practices developed for homogenous traffic by converting heterogeneous traffic to equivalen...

Modeling heterogeneous traffic flow

Cellular Automata (CA) modelling is extended to study the heterogeneous traffic observed in developing countries. In heterogeneous traffic, the physical and mechanical characteristics of different vehicles vary widely which in turn leads to complex traffic behaviour resulting in no-lane discipline. This nature of the heterogeneous traffic is modelled with the help of an improved discrete CA model. A detailed description of the methodology used in developing the basic structure of the CA model is presented and the modified methodology is used to generate different traffic scenarios. From the results, it is observed that with the help of simple updating rules along with typical heterogeneous traffic characteristics of the region, this model is able to reproduce real traffic behaviour. An added advantage is that the modified structure of the CA model can also be used to extract some basic traffic characteristics which are useful in understanding the heterogeneous traffic behaviour. The simulation model is finally validated using the flow and occupancy relationship obtained from the field.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/atr.5670430305

Cellular Automata Model for Heterogeneous Traffic

Increasing congestion due to rapid urbanization in developing countries like India necessitates the study of traffic flow for effective traffic management. Most of the traffic studies conducted in this regard were on the lines of methods used in developed countries. These studies were able to represent the traffic behavior only in a very limited manner. In developing countries traffic is composed of several types of vehicles ranging from cars with high speeds to low speed non-motorized vehicles. Microscopic traffic characteristics such as time headway and space headway are difficult to measure due to the heterogeneous nature (no lane discipline, and two or three small vehicles occupying one lane in lateral direction) of the traffic. Even using some of the macroscopic traffic characteristics such as density or occupancy, to study this kind of traffic may lead to erroneous results. Thus it is desirable to have a metric that can represent the heterogeneous nature of traffic in these conditions. Since varying...

Area occupancy characteristics of heterogeneous traffic

Data were collected at several locations of two-lane roads in different parts of India and were analyzed to study the speed, placement, arrival, acceleration, and overtaking characteristics of different types of vehicles. A computer program is developed to simulate the traffic flow on a two-lane highway incorporating all these characteristics. The simulation program is coded in Visual Basic language and has also been animated. A number of simulation runs were performed to determine the capacity of a two-lane road and to study the effect of traffic mix on capacity and speed. The passenger car unit (PCU) for an individual category of vehicles is calculated and the effect of directional split on capacity is evaluated. Capacity of a two-lane road under an all cars situation is estimated as 2,860 PCU/h. It increases to 5,600 vehicle per hour (vph) in case of all two-wheelers and reduces to 580 vph in case of all tractors situation. The capacity also reduces as the directional split moves away from an even split of 50/50 and this reduction is linear. It is further observed that the capacity of a two-lane road decreases as the proportion of three-wheeler, tractor, or heavy vehicle increases in the traffic stream. But, in the case of two-wheelers the capacity was found to increase with their own proportion. This is attributed to the small size of two-wheelers and their maneuverability.

Simulation of Mixed Traffic Flow on Two-Lane Roads

This paper critically reviews micro-simulation modelling applications for traffic safety evaluation with respect to the use of different simulation tools, the application of surrogate safety indicators under different aspects of road environments and crash considerations General input variables used to develop the models; key parameters for crash prediction; and calibration and validation approaches are explored in the paper The strengths and weaknesses of used simulation packages for traffic safety evaluation are also pointed out Moreover, recent advancements in the development and application of traffic safety micro-simulation model for safety assessment are also discussed Despite having a number of studies, there is still a significant void in the development and application of simulation model to evaluate traffic safety of non-lane based heterogeneous traffic environments that predominate in many developing countries The paper assessed the potential application of traffic safety micro-simulation model in heterogeneous traffic environments Finally, a number of potentially fruitful future research directions are highlighted

Micro-simulation modelling for traffic safety: A review and potential application to heterogeneous traffic environment

A stochastic discrete-event simulation model system for heterogeneous road traffic, which prevails on the Indian highway network, is presented. The original Swedish Road Traffic Simulation Model system, designed for motorized traffic, has been generalized to cover heterogeneous traffic that includes slowmoving nonmotorized traffic. The model has also been extended for narrow roads and covers roadwidths from 3.75 to 13 m with different shoulder types and alignments in flat, rolling, and hilly terrains. Submodels for the basic desired speed, power-to-mass ratio, overtaking gap acceptance and yielding probability distributions, passing speeds, and fuel consumption rates have been calibrated with extensive field data for subsequent validation of the simulation model. The output of the model has been intended primarily (a) to furnish relevant vehicle operating data for appraisal of individual road projects, (b) to constitute background data for a relevant level of service concept, and (c) ultimately to provide a basis for an appropriate policy on geometric design of rural roads in general. The model has been programmed in SIMULA-67 language using Jackson Structured Programming concepts. The results of validation exercises have been convincing; the model should be useful to decision makers for obtaining reliable data for investment analysis.

S P Palaniswamy

Papers

Indo-swedish road traffic simulation model: generalized traffic system simulator