An equilibrium route choice model with explicit treatment of the effect of intersections

This paper describes the implementation of a framework for incorporating detailed models of intersection operation into a user-optimal route choice model. It is assumed that signal settings are flow-responsive; this yieilds a combined route choice-intersection control problem, which is formulated as a non-separable network equilibrium problem with asymmetric cost functions. Such cost functions represent delays incurred by vehicles at intersections under various types of control (signalized, major/minor priority and all-way stop), and are based on an approach to capacity analysis widely used in traffic engineering practice, namely the methodologies of the 1985 Highway Capacity Manual and related amendments. The combined route choice-control problem is solved using a diagonalization algorithm; computational tests carried out on a real network indicate that the algorithm converges to a user equilibrium consistent with the control policy, despite violation of the sufficient conditions for convergence. The application also provides empirical evidence that the values of signal timing parameters, which are usually chosen solely on the basis of traffic engineering considerations, may have a substantial impact on the equilibration pattern. Finally, numerical experiments carried out to test the model for solution uniqueness suggest that ‘reasonably’ close equilibrium flow patterns arise starting from greatly different initial solutions. The modelling framework described in this paper could by typically applied in urban road networks for the assessment of alternative intersection control strategies, or, more generally, to carry out detailed traffic analyses and forecasts for the evaluation of TSM options.