1. Introduction

Transportation is not a science, but a field of inquiry and application. As such, it tends to rely on a set of specific methodologies since transportation is a performance driven activity and this performance can be measured. Transportation planning and analysis are interdisciplinary by nature, involving civil engineers, economists, urban planners and geographers (see concept 1). Each has developed methodologies dealing with their respective array of problems. Two common traits of transportation studies, regardless of disciplinary affiliation, are a heavy reliance on empirical data and the intensive use of data analytic techniques, ranging from simple descriptive measures to more complex modeling structures.

In some respects, transport geography stands out from many other fields of human geography by the nature and function of its quantitative analysis. In fact, transport geography was one of the main forces in the quantitative revolution that helped to redefine geography in the 1960s. Even if contemporary transport geography has a more diversified approach, the quantitative dimension still plays an important part in the discipline.

Thus, in addition to providing a conceptual background to the analysis of movements of freight, people and information, transport geography is much an applied science. The main goal of methods aims to improve the efficiency of movements by identifying their spatial constraints. It is consequently possible to identify relevant strategies and policies and provide some scenarios about their possible consequences.

2. Overview

There are various ways of classifying the methods that are used by transport geographers:

• Whether they are qualitative or quantitative.
• Whether they deal with infrastructures or flows.
• Whether it provides interpolation or extrapolation.
• Whether the technique provides description, explanation or optimization.
• According to the level of data aggregation, the nature of the assumptions or the complexity of the calculations).

The following two-by-two classification scheme has been chosen.

The top left cell identifies methods that are used mainly in transport geography. The best example of this is network analysis (also referred to as graph theory), which is used to study transport network form and structure, especially over time. For example, one could use network analysis to study the evolution of the hub-and-spoke configuration of airline service in North America.

• Transport geographers also play a key role in studying land use - transport interactions. Numerical models have been developed, which, over time, have become increasingly complex.
• Transport geographers are also interested in flow and location allocation models that can be used to define such things as school district boundaries or the location for a new retail outlet. These techniques are optimization procedures rather than methods for describing or understanding current transport systems.

The top right cell includes methods that are central to the discipline of geography, but are not restricted to the study of transportation systems.

• Map-making is the most obvious example of a geographic technique. Indeed, various types of maps are included in this web site. These include land use maps, depictions of transport infrastructure, isoline maps of transportation costs, schematics of transportation activity patterns, and many more.
• Geographic information systems (GIS), which are an outgrowth of digital cartography, provide a set of tools for storing, retrieving, analyzing and displaying spatial data from the real world. GIS technology has been applied to some large-scale transportation planning and engineering applications. More often, however, GIS are applied in a prescriptive way to small-scale problems, for example to plot optimal routes for buses, delivery trucks, or emergency vehicles.
• There are also various statistics that have been developed or modified by geographers to describe urban-economic systems. Examples include the Gini coefficient and indexes of concentration and specialization.

The bottom left cell includes various methods that are in general use in transportation studies.

• First, a diverse set of techniques is used in the four-stage urban transportation modeling exercise, the purpose of which is to understand and predict spatial patterns of travel in urban areas.
• Second, traffic surveys that are used to gather empirical information about movements.

The bottom right cell includes various techniques that are used in many different applications, including transportation analysis. Transportation analysts are not restricted to those techniques that have been developed with transportation in mind. In fact, many methods that were initially developed for other problems have widespread use in transportation studies.

• Some methods are used to collect primary data, e.g. questionnaires and interviews, while others are used to analyze data. Some of the analytic techniques are straightforward to implement and interpret; graphs (e.g. scattergrams, distance-decay curves) and tables (e.g. origin-destination matrices) are two examples. Others are more complex, e.g., inferential statistics like the t-test, analysis of variance, regression and chi-square.
• Increasingly, transportation studies are concerned with impacts and public policy issues. Various types of impacts are considered, including economic (e.g. community development), social (e.g. the equity of access to essential services), environmental (e.g. air or water pollution) and health (e.g. road accidents). The broad fields of environmental impact assessment , risk assessment and policy analysis are relevant to these issues.