1. General Information

Transport geographers must learn to analyze complex situations such as those that arise in the context of transportation planning, such as creating new infrastructure or managing existing networks and fleets. An example of such a process is the selection of a route for a new regional road, which is a classic example of the impacts of multiple geographical constraints over the nature and extent of a transport service. The route selection process of this exercise will abide to a multi-criteria decision-thinking process where a final decision is made by considering different types of information.

An hypothetical Ministry of Transportation is planning the construction of an highway between two cities (Eastown and Westown), roughly 112 miles apart. The government wants to undertake a feasibility study which will determine core transport planning elements such as construction costs, economic benefits and environmental impacts. This project has thus been forwarded to the Transportation Planning Bureau (TPB), which responsibility is now to provide an appropriate route and a justification of this choice.

As the head of the TPB, your task is to design an highway route linking the previously identified start and finish points. You must insure that the road must be the shortest, the least expensive, the least damageable to the environment and servicing the largest number of people. Some criteria are self reinforcing, such as road length and economic benefits, while others are mutually exclusive, such as road length and environmental damage. An appropriate balance must be found, which tries to satisfy diverging interests. Once a suitable route has been selected and approved, the Ministry of Transportation will start the bidding process for construction contracts.

This exercise has been designed to be completed manually or by using a GIS:

• The manual completion of this exercise requires the downloading and printing of the appropriate PowerPoint slides (left). A ruler has to be used to measure distances.
• The GIS completion of this exercise represents an useful introduction to the application of GIS-T methodologies to solve a transport problem. An ArcView GIS dataset containing all the required layers and an accompanying MS Word file (ZIP file) has been provided (left). A basic understanding of ArcView GIS, notably polyline creation and editing as well as spatial querying is required.

2. Spatial Constraints

Several GIS layers illustrating different constrains of the region where the highway is to be built have been prepared by different ministries and forwarded to the Transportation Planning Bureau. Each has been plotted as a map pertaining to a specific constraint category. They include:

• Basic constraints. No road shall step over urban centers identified as dark gray circles on maps. An urban center is considered to be serviced when the road touches its area of influence (light gray circle). Also, the highway must be composed of continuous straight lines (no branching).
• Physical constraints. For simplicity, physical and environmental constraints are presented as grids. This map contains the location of rivers as well as rugged terrain cells. It will be used to establish basic construction costs.
• Environmental constraints. This map identifies sensitive zones (grid) with an ecological value such as parks, forests or marshland. An attempt has been made to rank this value for each cell on a scale of 0 (no value) to 5 (very high value).
• Economic potential. This map portrays the economic value of each cities as a sphere of influence proportional to their population. There are also industrial development zones that would benefit from being linked by a road.
• Political constraints. They are presented as a dichotomy between actors in favor and against road construction. Many cities are in favor of road construction while some landowners are strongly opposed.
• Composite Map. This map contains an overlay of all the layers involved in the decision-thinking process for the construction of the highway.

3. Result Table

The evaluation of the quality of the route selection will be performed according to 3 criteria, which are the length, the cost, and the environmental score. A route may have a high score for a criteria, but a weak score for the others. The goal is to have a high score for as much criteria as possible, which requires a well-studied itinerary. The concept of Pareto-optimality explains well the framework for multicriteria decision-making for this problem. Results should be filled on this table: