Modelling of traffic flow and air pollution emission with application to Hong Kong Island

In this study, we propose a Lagrangian model for the simulation of traffic flow on a complex road network. This simple approach is quite efficient if adequate road network data are available and statistical constraints are applied to confine the model behavior. We have established a traffic information database for Hong Kong Island and applied the model for traffic flow simulation. It is shown that by specifying three types of traffic routes (random turn, preferred turn and shortest path) and providing traffic flow data at selected stations, the model is capable of simulating traffic flow on the road network. This is confirmed by comparing model simulated and observed traffic flow patterns at several monitoring stations. The simulated traffic flow is then used as the basis for the estimation of traffic induced emission of air pollutants on the island. Using empirical emission factors for a number of vehicle categories, the emission rates of major air pollutants, CO, NOx and PM10, are estimated. The predicted emission rates are compared with measurements for several air quality monitoring stations.