1. Introduction
1.1 Purpose and structure of this guidance
Any transport model is a tool for understanding and assessing the likely impacts of changes in the drivers of transport, such as transport supply, demographics or land use. In this context, transport modelling can assist with decision-making about the future development and management of urban transport and land use systems.
This document provides guidance for developing and applying strategic highway and public transport models when appraising major transport initiatives in the urban context
This document is not intended to be a detailed technical treatise on developing individual components of a transport model, but rather a succinct, practical and pragmatic reference for developing, applying and assessing transport modelling. Detailed information on transport modelling theory and methodological approaches can be found in transport modelling references.
The urban transport modelling guidelines represent the minimum level of recommended acceptable practice and are provided to:
- Establish principles of good and consistent transport modelling practice, rather than being prescriptive on transport modelling methodology
- Ensure a consistent understanding in the application of transport modelling
- Provide a better understanding of the transport modelling process.
This document contains five sections:
| Section | Summary |
|---|---|
| Overview of transport modelling | This provides an overview of the transport modelling process and high level issues. This material is readable at a project management level. |
| Model design | This section covers standard model structures and techniques for modelling travel demand and transport networks. This material is aimed at a technical level. |
| Data collection | This covers data collection, types of data, collection approaches and techniques. This material is aimed at a technical level. |
| Model development | This covers the techniques used in the development of transport models. This material is aimed at a technical level. |
| Forecasting and evaluation | This covers the use of models for forecasting and evaluation. This material is aimed at a technical level. |
1.2 Role of transport modelling
Transport systems play a critical role in facilitating the way we work, delivery of the goods we use and facilitating the social and recreational activities we enjoy. The benefits of accessible and efficient transport systems come at a cost. The transport infrastructure requires land and can cause severance in our communities. Our travel consumes resources and generates emissions and noise that impact on our health.
Decisions on whether and how to intervene in our transport systems can thus have far reaching consequences for our economy, environment and society. Effective decision making thus requires an appreciation of the wide range of consequential impacts, Major infrastructure can take several years to construct and will exist for many decades. The information required to understand impacts requires forecasts many years into the future and is subject to the risks and uncertainties inherent in forecasting.
The role of transport models is to provide structured forecasts that can be interrogated to provide information on implications of transport interventions. The model outputs are used both to
- establish a structured understanding of the performance of the transport systems, today and forecasts of the future, from which to identify the need to consider interventions; and
- compare the performance of transport systems with and without interventions to understand their merits.
There are two particular challenges for the transport modeller. The first is to balance the complexity and cost of the modelling and forecasting tasks to the decision making needs. Too much complexity is simply a waste of resources. Too little and the outputs cannot be used for the intended purpose. Secondly is the requirement to explain the forecasting uncertainty to allow decision makers to understand the reliance that can be placed on particular outputs and the inherent risks.