A region is divided into m residential and central business districts. Each district is represented by a node, and the nodes are interconnected by links representing major routes. People living in the various districts go to their business in the same and/or at other districts so that each node attracts and/or generates a number of trips. In particular, let a_ij be the number of trips generated at node i with final destination at node j and let b_ij be the time to travel from node i to node j . It is desired to determine the routes to be taken by the people living in the region.

a. Illustrate the problem by a suitable network.

b. Develop some measures of effectiveness for this traffic assignment problem, and for each measure, devise a suitable model.