Driver behaviour and traffic modelling. Are we looking at the right issues?

Although much attention has been given to the simulation and modeling of driver behaviour, and comparison and testing of differing algorithms (such as car following) is now performed, there are several assumptions in use regarding micro-modeling that may not be correct. These could have important implications to our ability to model the impact of ITS (Intelligent Transport Systems), in particular, in-vehicle systems. In this paper we will examine four assumptions regarding car following models that may be in need of revision: 1) drivers adopt constant time headways and use 'safe' following distances, 2) there is a lack of data against which to undertake calibration/validation, 3) short time steps allow more realistic simulations of dynamics, and 4) that there are important' Chaotic patterns' in car following.