Why is a transport demand policy so difficult when it is so important?

In the next week the Commission on Travel Demand will have its final evidence session on ‘decision-making’. In advance of that and my talk at the Landor Local Transport Summit I wanted to share some thoughts about why demand policy seems to have slipped off the transport agenda. This seems particularly troubling given the really limited progress which seems to be being made on climate change emission reduction and air quality.


Nothing about this image screams “lets not worry about travel demand”. The 2015 National Road Traffic Forecasts showed an increase of between 19% and 55%. The CCC works on a central or most likely projection from the Department. Looking at the NRTF this would be the scenario with growth of 34%. On these grounds alone, demand matters. For every % over the core scenario the significance of the amber and red areas in the CCC graph is magnified and for ever unit under it is reduced.

However, we do not have a clear policy on travel demand. This, I believe, stems in part from the economic traditions underpinning transport analysis. Here, demand is a measure of consumer preferences in transactions with more demand general seen to be a good thing (subject to the caveats of well performing markets and full externalities being paid which we seem happy to hold out as a possibility. Sometime).

Demand is also rather curiously, yet rather importantly, held to be somehow ‘out there’ and independent of policy. By this, I mean that our approach to looking at demand in the future tends to try and hold policy constant and ask what impact important exogenous variables could have such as oil price, GDP and population. Only then do we look at the extent to which this demand might be accommodated or not. This is worldview one or the “two moons” part of the figure below.


Three worldviews of demand and policy

This might be an overly tough critique of the way of things today. It could be argued that in oil price sensitivities there are assumptions of pricing policy from government and it is also the case that some policies are seen to be able to impact on demand – such as the Committee on Climate Change’s assumption that behaviour change could reduce travel demand by 5%. This corresponds to worldview 2 or the very partially overlapping moons.

However, is that all that matters? If we look again at the NRTF, the highest growth scenario identified could only meaningfully be brought about if the growth in demand were supported by the same kind of infrastructure or supporting policies that were in place in the last period where such growth was seen back in the 1980s and early 1990s.


Similarly, Scenario 3 assumes a continued reduction in trip rates. Not all of this has been the result of transport policy for sure. However, it is easier to imagine this scenario unfolding in a policy setting where much greater attention was given to localisation, virtual communication and trip chaining through densification of activities than it is in a world where the focus is on very significant investment in major inter-urban infrastructure.

Demand has to be more strongly shaped by policy than is currently considered or allowed to be seen to be. That is part of the explanation as to why different countries have different levels of per capita travel. It is perhaps convenient, more than realistic to hold the position that demand futures are somehow independent of policy futures (see Foresight in Action for a great short read on this).  It means you may not need a policy on demand reduction because it is not something you have agency over. This fallacy can be picked apart by looking ahead. There are clearly policy choices to be made about how we welcome autonomous vehicles to our roads, how we regulate mobility service providers such as Uber and Lyft and what kind of a service Mobility as a Service can become. It is not all determined by policy – but it is not free from policy.  It also will not be allowed to unfold the same way in every city or country. That will clearly affect the services provided, how they are used and what they get used for – i.e. demand. This is the third world view of more highly overlapped circles in the diagram. This recognises the inter-relationship between demand and policy. As the framework conditions of policy shape the demand that develops so too does policy respond to the levels of demand which emerge. This can work to drive up or bring down demand.

I started out by suggesting that it is imperative that we act to reduce demand if we are to meet our climate objectives. To end on a positive note, IF we accept that policy matters to shaping demand then we can plan by asking questions that start with “What kind of a future do we want to create?” rather than starting with “What kinds of demand do we need to accomodate?”. I’m looking forward to hearing more about what needs to be done to change rather than reinforce the current pathway.



2 responses to “Why is a transport demand policy so difficult when it is so important?”

  1. Gabriela Baesse says :

    Hello Dr. Marsden.
    What a great text! I’m doing my master in urban and regional studies in Universidade Federal do Rio Grande do Norte in Brazil.
    Could you please recommend me some article about this relation between urban mobility’s policy and travel demand?
    Thank you very much! You have a great content here.

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