The Geography of Transport Systems

Previous Next


Gravity Model Exercise Basemap


Gravity Model Exercise Data and Results


Chapter 5 - Applications (PowerPoint)

Exercise: The Gravity Model

Author : Dr. Jean-Paul Rodrigue

1. General Information

The location of economic activities in generates a transport demand that is represented geographically by a set of origin-destination pairs. Gravity-type spatial interactions models offer a methodology to appraise the transport demand between a set of locations. For a transport company, knowing this information is very useful to the processes of scheduling vehicles along routes. This exercise involve the application of a gravity spatial interaction model for scheduling the activities of a fictive airline company.

A large airline company (Air Modal inc.) hired a consultant in order to help them reorganize their international links and to develop new service strategies. Indeed, the company wants to know the potential demand of air transport between and inside continents. Knowing this demand, it will be able to assign its flights more efficiently and see where growth perspectives are the most attractive. The following information is available to apply the spatial interaction model:

Emission and Attraction Data
  Urban population (2000) Lambda Alpha
Europe 545,000,000 1.00 1.00
North America 239,000,000 1.08 1.08
Oceania 21,000,000 1.07 1.07
Latin America 391,000,000 1.01 1.01
Africa 295,000,000 0.91 0.91
Asia 1,352,000,000 0.99 0.99

Both the lambda and alpha indexes have the same value, since it is assumed that on a yearly basis all the passengers are going back to their place of origin. The reality is more complex as some passengers may do multiple destination trips (e.g. North America to Europe to Asia and then back to North America), while others are doing a one-way flight only (immigration). The values of lambda and alpha are higher for Latin America than for Europe, which reflects better land based transport alternatives for Europe (mainly train) as well as a more compact location of the population.

Average Distance Between Destinations
Distance (in km) Europe North America Oceania Latin America Africa Asia
Europe 1,000 8,000 15,000 9,000 4,000 12,000
North America 8,000 2,000 14,000 8,000 11,000 12,000
Oceania 15,000 14,000 2,000 14,000 14,000 13,000
Latin America 9,000 8,000 14,000 3,000 7,000 17,000
Africa 4,000 11,000 14,000 7,000 3,000 10,000
Asia 12,000 12,000 13,000 17,000 10,000 3,000

The value of the k coefficient is 0.00001 (yearly value) and the friction of distance (beta) coefficient is 1.34 between all origins and destinations.

2. Results

Results must be presented as a report to the board of directors of Air Modal inc. This report must include the following:

The exercise can be extended to include more complex tasks:

Copyright © 1998-2008, Dr. Jean-Paul Rodrigue, Dept. of Economics & Geography, Hofstra University. For personal or classroom use ONLY. This material (including graphics) is not public domain and cannot be published, in whole or in part, in ANY form (printed or electronic) and on any media without consent. Permission MUST be requested prior to use.

04/07/08