April 07, 2005

Solutions: CV and TDM measures

As I wrote my previous two contributions, I was reminded of a text I read in the Victoria Transport Policy InstituteĀ“s online TDM encyclopedia, about two possible solution strategies concerning traffic-related emissions.

It is clear that autonomous growth of mobility demand, combined with a need to combat congestion and stricter limits on air pollution levels makes for tough policy choices for authorities.

In environmental science, it has long been said that in order to reduce environmental impacts of activities, technical as well as behavioural developments need to take place.

In the TDM encyclopedia, the technical measures are called Clean Vehicle, or CV measures, and the measures targeting behaviour are called TDM, or Transport Demand Management measures.

Typically, CV measures lead to a limited number of benefits and entail a limited number of costs, and, crucially, few actors that are bearing these costs.

On the other hand, TDM measures typically lead to multiple benefits, and carry multiple costs that would affect multiple actors.

This makes TDM measures more likely to run into all sorts of institutional and political barriers.

In the issue addressed in the previous two contributions, this is neatly illustrated: It is politically easier to implement a technical solution (German cities also take this course of action, see "See you in court!") than to introduce a set of TDM measures that would induce people, or rather voters, to change their behaviour (for instance, to introduce or promote PAYD, to change speed limits, etc.).

This inclination towards technical solutions carries two risks: Firstly, the effect of these changes may be prone to so-called kick-back, or volume effects: for instance, the Dutch vehicle fleet has become more fuel-efficient in the past decade, but also more weighty (bigger cars and engines): net environmental gain is very small.
Secondly, since technical solutions typically address but one problem issue, other issues may not only remain unaffected, but even be made more severe by this type of measure. For instance, when combating traffic jams with road building, environmental problems are likely to worsen.

That is why, in my opinion, TDM strategies are also needed.

Christof

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