Seeking info on induced traffic

A fundamental issue we run into when advocating a shift in transport investment from road building to cycling, walking and PT is that the evaluation models used by Govt ignore induced travel.

I am seeking NZ or overseas research which challenges the belief that road building is good for the economy.  Can you add to this list?

Here's what I have found so far:

1. Myth #1. "New roads are good for the economy"
In order to investigate this commonly held assumption, the UK's Department for Transport commissioned the SACTRA Report1, it concluded that the linkage of new roading with economic growth is "weak and disputed".

Furthermore, the study found that economic effects of a roading project are significantly affected by local circumstances and conditions. A new road may actually make areas worse off, as businesses use the new link to relocate out of the region and residents are encouraged to drive further a field for their shopping, work and recreation.

The urban sprawl encouraged by new motorways can mean significant infrastructure costs for local councils and their ratepayers, who may struggle to afford the additional infrastructure required such as stormwater, sewerage, footpaths, lighting, libraries, etc.

A strong and resilient economy requires a balanced transport system. This is best achieved by using the transport planning hierarchy where each of the various transport modes is prioritised based on their sustainability and efficiency. Such an approach encourages good town planning, public transport, walking and cycling before building new roads.


2. UK's Standing Advisory Committee on Trunk Road Assessment (SACTRA) commissioned a 3 year study which searched for and reviewed the research and found "Empirical evidence of the scale and significance of such linkage is, however, weak and disputed." 

3. Simon Kingham's article in 'The Press' covers induced traffic, congestion, public transport and transport policy, at

4. A new research report published by the NZ Transport Agency (RR350: Economic development benefits of transport investment) "reviews the major approaches for assessing national and regional economic benefits, as well as the potential distributional implications of transport induced benefits.  The paper assesses whether transport influences national and regional economic development, and if so, how this is role is best asserted." This report is available at  A hard copy will be available to be borrowed from the CAN Library.


I've added a link to a just-released report from NZTA.
Robert Ibell
04-972 2552

Here's a key finding:

Role of transport investment in promoting economic development

This chapter sought to address the following key question:

• Question 3.1: Are there particular features of transport investment (in general) that make it especially effective (such effects maybe not fully reflected in SCBA or alternative methods of assessment) in promoting/increasing national (and regional) economic growth?

The conclusions and observations of this chapter can be summarised as follows:

• Evidence for a ‘special role’ in respect of transport infrastructure investment’s economic growth effects (as opposed to effects generated by other public spending, such as on education or health) is limited. The high rates of return to transport investment claimed by some past studies are likely the result of statistical correlation or other model specification issues.

• Likewise, there is nothing ‘special’ about investment in transport infrastructure from a regional perspective. While there is some evidence regarding the responsiveness of growth to investment in transport infrastructure, this is no less true then other forms of public spending. It is unlikely that investment in transport infrastructure will have dramatic effects on regional economies.

• In general, development of transport infrastructure is a necessary but not sufficient condition for national and regional economic development and growth.

• The incremental economic gains of further investment in transport infrastructure in developed economies are likely to be small. Arguably, there is a spectrum within which some developed economies may experience greater gains more than others, but solid evidence to this effect is lacking.