18: Dynamic Equilibrium Network Design

The problem of designing a road network optimally in respect of benefits of travel and costs of construction whilst taking into account travellers' likely response to variations in the design is well established as one of substantial importance and yet is known to be difficult (Yang, 2001). The importance of taking account of travellers' likely response is highlighted by the extreme example of Braess' paradox (Murchland, 1970). This shows that when designing a road network, supposing traffic flows either to be constant or to respond neutrally can lead to decisions that, whilst intended and expected to improve network performance, cause deterioration. The established literature on this topic uses static assignment according to either the deterministic or the stochastic equilibrium principle to represent the influence of the design of the network on the amount and character (including route) of travel, and the effects of this on the costs incurred.