A microscopic model that describes the behaviour of vehicles on a multi-lane carriageway has been developed at TRL for the Highways Agency. The model is known as SISTM (the SImulation of Strategies for Traffic on Motorways) and has been calibrated during its development by using traffic data collected from a variety of motorways in the UK. However an initial investigation into the ability of SISTM to replicate speed-flow behaviour on the M25 found that whilst congestion for traffic was reproduced well, there was no scope for generating and reproducing a shockwave. This paper describes the reinterpretation of the car-following model into terms more relevant to observed traffic behaviour and in particular the propagation of shockwaves. The stability and sensitivity of the model to its constituent parameters was examined by developing vehicle classes with behaviour regulated by various aspects of the car-following theory. Systematic exploration of the algorithm led to the successful replication of shockwaves and a series of recommendations for their implementation within SISTM. (A)
Abstract