Vehicular Traffic Simulation

CHAPTER 3: SIMULATION OF TWO-LANE TRAFFIC FLOW MODEL USING MODIFIED CA

3.1 INTRODUCTION

Efficient vehicular transport of people and goods is of vital importance to any modern society. In densely populated areas the capacity of the road network is often at its limits and frequent traffic jams and congestions cause a significant economic damage. Modeling traffic transport problem is very interesting and important for its dynamics and serious dramatic consequences in real life. Mathematical modeling and computer simulations play important roles in studying the impacts of various policies on vehicular traffic. Modeling and simulation techniques are integral components of intelligent information systems being used in advanced

2007). In periodic category the lead vehicles at the end of the road reenter the system at the beginning of the road, whereas in open category the vehicles at the end of the road are deleted from the system and new vehicles allowed to enter the beginning of the road. While open boundary rules are more adaptable for realistic road network, the periodic boundary conditions are used when the roads can be hypothetical.

3.3 CA MODELS FOR SINGLE LANE TRAFFIC FLOW

3.3.1 The Model and its rules

Designing a simulation model as simple as possible, the most radical way is to use integer variables for space, time and speed. Such a simulation model is called a cellular automaton. In CA traffic flow model, the road is divided into L cells, and a vehicle has a length of l cell(s).It is usually assumed that the length of a vehicle is 7.5 m. The length of a cell is given by the minimum space headway between vehicles in jam. This philosophy is represented by the following four rules in the NaSch Model. Rule 1. Acceleration : ;

Rule 2. Deceleration : ;

Rule 3. Randomization : with probability

The authors attempt to more accurately simulate the behavior of drivers which have come to a complete stop in traffic jams on the highway. Cars which have velocity 0 either accelerate at their first available opportunity (as soon as there is an empty space ahead of them) with probability , or on the time step immediately after that with probability .Otherwise, they follow the NaSch model. This scheme is intended to reflect the fact that drivers take longer to accelerate from a complete stop, perhaps because they do not immediately notice the car ahead of them moving or because of the slow pick-up of their car’s engine. So the BHJ model is essentially the NaSch model with the addition of ‘slow-to-start’ rule (Clarridge et al.