THEME 10 - TRAFFIC DEMAND MANAGEMENT
Traffic demand management (TDM) (sometimes known as ‘mobility management’) covers a range of measures aimed at reducing the adverse impacts of car use. They are complementary measures to spatial planning (and vice versa). TDM deserve distinct detailed coverage - this is a wide topic area – and there are a number of further resources available that cover some of the issues (for example Leeds University’s KonSULT database, the VTPI’s Online TDM Encyclopedia and Oxford University’s IMPACT database).
The commentary here is necessarily brief, in the context of supporting mechanisms to spatial policy. There are often overlaps in definition (‘TDM measures’ sometimes include land use planning; many of the organisational/behavioural change measures, and wider, are known as smarter choice ‘soft’ measures (after Cairns et al, 2004). For the purpose of this guide, we structure discussion of TDM interventions as below.
Organisational and operational
- Travel plans (workplace, school, residential, area-wide), personalised travel planning.
- Car pooling, car sharing and car clubs.
- Company work hours, flexible-working, home working.
- Home retailing and delivery.
- Tele-activities and interaction.
- Marketing/media campaigns.
- Transport optimisation, peak congestion avoidance.
- Slower speeds and ecological driving styles.
- Pricing regimes, including (where applicable) road user cordon charging, area-licensing schemes, continuous charging.
- Vehicle ownership taxes.
- Public transport investment/subsidy.
- Parking charges.
- Bicycle investment/subsidy.
- Improved public transport facilities, including (where applicable) National Rail, Underground, light and ultra light rapid transit, guided bus and bus, etc.
- Demand responsive transport.
- Park and ride.
- Improved walking and cycling facilities.
- Road space re-allocation and priority, traffic calming, access control and restrictions.
- Streetscape design.
- Parking (discussed as a distinct topic in theme 11).
1. To what extent can traffic demand management influence travel behaviour?
TDM measures, including smarter choice behavioural measures, may have more scope to influence travel behaviour than is commonly assumed (Cairns et al, 2004; Goodwin et al, 2004). The evidence suggests that, within 10 years, smarter choice measures have the potential to reduce national traffic levels by around 11% (Cairns et al, 2004; Cairns et al, 2008). The right support and policy context is, of course, critical to resulting travel changes – including infrastructure provision, etc. Demographic factors and income are key drivers of behavioural change but are exogenous factors beyond the scope of TDM policy interventions. Travel plans and personalised travel planning are one of the few tools that can influence behaviour in the existing land use stock. There are also evolving issues over translating the success of smarter choice measures to the wider market, i.e. beyond the cohort that show propensity to change, and in further understanding the rationales for mobilities and travel behaviours.
Significant behavioural changes have been observed in the UK Sustainable Travel Demonstration Towns as a result of packages of ‘soft’ measures. These changes included increases in public transport trips (13-22%), walking trips (17-29%), cycling (25-79%) and a decrease in car trips (11-13%).
“Local authorities should be aware of the potential for a congestion charge or parking levy to increase pressure for dispersal of development away from the charged areas to locations which would be likely to be more car dependent. They will therefore need to pay particular attention to the areas to be included in any scheme, the scale and exemptions for charging, the times when charges apply, and the use to which proceeds are put, to that the overall effect of measures promote town centres as preferred locations for development. Planning policies should be used to continue to resist dispersal pressures.” (PPG13, paras 70-71)
“The Government considers that travel plans should be submitted alongside planning applications which are likely to have significant transport implications, ..,” (PPG13, para 89)
“Demand management covers the range of techniques used to reduce traffic generation. Having regard to the guidance set out in PPG13, paragraph 89, developers, working in partnership with local authorities (where appropriate), must submit plans for the implementation and maintenance of measures that will minimise the traffic generated by their development. This is likely to be through travel plans. These will include, but will not be limited to, measures to manage car use, particularly by single occupants. Examples of such techniques may include tailored provision of public transport, car sharing/pooling, parking control, and the encouragement of cycling and walking.” (DfT Circular 2/07, para 33)
Planning Checklist: TDM
Practitioners are advised [as a complement to their spatial locational strategies] to develop a rigorous TDM strategy to help develop sustainable travel behaviour.
10.1. At the regional, sub-regional and local levels, this means developing and implementing a strategy, including the strategically and locally important infrastructural, organisational and financial policy levers. This will include major walking, cycling and public transport investment, ‘smarter choice’ behavioural measures, marketing campaigns and potentially pricing and subsidy regimes.
10.2. The Sustainable Travel Demonstration Towns pilot has included investment in many of these measures and illustrates the type of strategies that are effective in reducing car-based travel (DfT, 2009b). This type of package of interventions should be carried out in urban areas and new developments across the UK.
Evidence and Examples
The evidence given here is necessarily selective, but gives an introduction to the research on this topic. More details are found in the background technical report.
Goodwin et al (2004) summarise some of the TDM-related research over recent years, with Cairns et al (2004, 2008) covering the smarter choice interventions. Key findings include evidence that induced traffic due to road building exists and that, conversely, reductions in road capacity often lead to ‘disappearing’ traffic. The evidence is that, within 10 years, smarter choice measures have the potential to reduce national traffic levels by around 11%, with reductions of up to 21% in peak period urban traffic. The measures typically also generate good cost benefit ratios. The Department for Transport has developed a number of guidance notes on the application of smarter choices.
Much of this type of debate is now being discussed in terms of rationales for mobilities (Urry, 2007), including sociological and psychological dimensions to travel behaviour. Deeper understandings may help us be more successful in encouraging greater sustainability in travel.
While the scope for changing travel behaviour through infrastructure, organisational and operational, and financial mechanisms is wide, directions of change are not always symmetrical (i.e., an increase in bus fares may reduce ridership more than an equivalent decrease in fares would increase ridership due to different elasticities) and are likely to vary over time (i.e. the short-term impact of higher fuel prices maybe be less than the long term impact). TDM interventions may also influence land use change over the long term as decision makers adjust their strategies to available infrastructure, behavioural norms and price incentives. In terms of financial measures, dynamic approaches to modelling price elasticities have shown strong differences in short-and long-term elasticities and also differences between urban and rural respondents. In several cases, the long-run elasticity was much higher than had previously been assumed (Goodwin et al, 2004). [‘Elasticity’ is a measure of the sensitivity of volume of travel to changes in price or speed or other ‘costs’ of travel.]
Several on-line resources describe the suite of measures that can be considered as part of a TDM policy package. In the UK, the Knowledgebase on Sustainable Urban Land Use and Transport (KonSULT) developed by the Institute for Transport Studies at the University of Leeds covers attitudinal and behavioural measures, infrastructure management and pricing in considerable detail as well as related topics.
The Victoria Transport Policy Institute (Canada) provides an Online TDM Encyclopaedia that explains the vast array of potential TDM interventions. Appropriate measures obviously vary by context and need to be considered as part of a package of TDM policies aimed at reducing travel by car in favour of more sustainable modes.
Oxford University’s IMPACT database also provides a developing catalogue of evidence on the potential for carbon reduction in the transport sector, which includes reference to TDM measures.
Further reading here
Milton Keynes / South Midlands - Buckinghamshire County Council and Aylesbury Vale District Council have developed an integrated TDM scheme to achieve their “vision” of a traffic free zone for the market square supported by measures to encourage more people to use bus services, cycle and walk to the town centre. The councils have obtained £14m of funding to implement the scheme.
North East of England - In the North East, the potential benefits of ‘smarter choices’ in terms of generating a shift to more sustainable travel behaviour – generally within an established urban structure – is being promoted pan-regionally by the Northern Way and the local authorities in the area.
Greater Manchester - The Greater Manchester TIF bid and later funded work exemplifies good practice in TDM as infrastructure investment, operational change and pricing mechanisms were organised into a comprehensive package. This was also reflected in the Local Development Frameworks of the individual metropolitan councils.