THE GEOGRAPHY OF TRANSPORT SYSTEMS
Source: adapted from R. Tolley and B. Turton (1995) Transport Systems,
Policy and Planning: A Geographical Approach, Burnt Mill, Harlow
Essex: Longman Scientific & Technical, p. 54.
Effect of Transport Costs on Route Selection
The above figure presents a route selection problem between two locations (origin a and destination b) and involving two modes; land and sea. It requires selecting one port out of a choice of four (p1 to p4) and assumes that there is a direct land connection between a and each port. The choice of the route is the outcome of comparative operating costs.
- The first route selection (1) assumes equal transport costs over land and over sea; R{C(sea) = C(land)}. In this case, the costs of moving from origin a to port p3 are equal to the costs of moving from port p3 to destination b. In reality, the direct route from origin a to destination b is not the best solution because it does not take account of transport costs differences between land and sea.
- The second route selection (2) assumes two possibilities. In the first, sea transport costs are higher than land transport costs; R{C(sea > C(land)}. Under such an assumption, route R1 minimizes sea transport costs. For the second possibility, land transport costs are higher than sea transport costs; R{C(sea) < C(land)}. Route R2 consequently minimizes land transport costs.
- The third route selection (3) is the optimal solution, not too far from the reality. It considers that land transport costs increase at a higher rate than sea transport costs, but that land transportation costs are initially lower. Land transport can thus be more advantageous than sea transport for a short distance, enabling to use port p2 instead of port p1.