A Relaxation-Based Heuristic Approach for the Mixed-Integer Evacuation Model
A basic urban evacuation model is presented in Chap. 3 with the extensions of the possibility of waiting and the reassignment of the traffic routing only to one-way streets. In this chapter a heuristic solution approach will be presented for the urban evacuation model which relaxes some constraints and integrality in a first step. In a following step based on a solution of the relaxation, feasibility is generated for the considered urban evacuation model. We will consider the two-way case (compare Bretschneider and Kimms 2011) and the one-way case. The two-way case is more difficult to handle, so it is considered first. The one-way case can be derived from the two-way case. The approach will be explained for the urban evacuation model without waiting presented in Sect. 3.2 with the objective function (3.1) that minimizes of the average evacuation time. For the variation of the evacuation model with waiting on arcs the relaxation approach can be applied analogously.