BRAESS PARADOX - SOME NEW INSIGHTS

This paper examines some properties of the well-known Braess' paradox of traffic flow, in the context of the classical network configuration used by Braess. The paper shows that whether Braess' paradox does or does not occur depends on the conditions of the problem; namely, the l ink congestion function parameters and the demand for travel. In parti cular, this paper shows that for a given network with a given set of l ink congestion functions, Braess' paradox occurs only if the total dem and for travel falls within a certain intermediate range of values (th e bounds of which are dependent on the link congestion function parame ters). The paper also shows that, depending on the problem parameters, adding a new link might not lead to a reduction in total system trave l time, even if users are charged the marginal cost of traveling. On t he other hand, there are ranges of values for the problem parameters f or which the new link reduces total system travel time, as long as mar ginal cost pricing is implemented. (C) 1997 Elsevier Science Ltd.