Probit-Based Sensitivity Analysis for General Traffic Networks

The probit-based stochastic user-equilibrium (SUE) model is widely recognized as one of the most intuitively robust traffic network assignment techniques. Its advantages include explicit consideration of random perceptual differences in utility across the driver population and the ability to take proper account of the correlations in these utilities between overlapping routes, which the simpler logit SUE is unable to do. Its main drawback is the potentially heavy computational demands of the method, but various efficient approximation methods have been observed to provide reasonable solutions. This computational complexity was previously, however, thought to preclude a consideration of the sensitivity analysis of probit-based SUE, whereby an approximation to changes in the equilibrium solution is deduced as its input parameters are perturbed. An efficient computational method for performing such an analysis in general networks is described. A simple network example is described in detail to illustrate the method, and it is followed by a larger network example that further demonstrates the practical nature of the method.