Road traffic demand has more than doubled over the last 25 years, and further growth is expected. This will lead to greater congestion, with associated economic and environmental costs. Calls are increasingly heard for the introduction of policies and targets for traffic reduction. Therefore, policy-makers need to know what measures are most effective, and whether their socio-economic and financial impacts are acceptable.
START had three main objectives:
- to quantify the impacts of measures to reduce road travel and assess the wider effects and barriers to implementation;
- to assess the extent to which travel reduction strategies may affect the financing of road infrastructure;
- to recommend an Action Plan of travel reduction policies for Europe.
The project found that the most cost-effective policies to deal with congested traffic in cities are based on pricing. Road pricing per kilometre or at a city cordon is favoured, while parking charges have a less direct impact and may not work where there is extensive private off-street parking within the congested area. Subsidies to urban public transport are considerably less effective.
On inter-urban roads, the use of tolls to reduce traffic is more problematic. The dominant response from users is likely to be a diversion to alternative routes rather than a switch to alternative modes or a reduction in the total amount of travel. This is likely to be counter-productive in terms of environmental and congestion costs. In addition, it would create a barrier to the use of private finance in the development of road infrastructure, requiring the public sector to take on the financial risk associated with uncertainties in future traffic levels.
In general, push measures to deter the use of vehicles (e.g. fuel taxes) are seen as more effective than pull measures (e.g. improving alternative modes). Nevertheless, successful strategies are likely to contain a mixture of both ‘push’ and pull measures, with the revenue from the former being used to fund the latter. Experience has also shown that a mix of different types of measure works best – pricing, capacity management, public transport, telecommunications and land-use planning.
Push measures face problems of public acceptance. However, research has indicated that as people become better informed about the likely cost-effectiveness of ways of dealing with transport problems, their opposition to restraint measures tends to decrease.
The project devised four scenarios of traffic reduction in the short and medium term, identifying packages of measures required to achieve certain economic and environmental objectives. Compared to do-minimum and green strategies, the best outcome was assessed to result from a strategy based on internalisation of congestion costs and environmental costs by the road user.
Most of the reported travel reductions are only of the order of one or two years’ growth in (unconstrained) demand. Policy actions may still be desirable, but the lesson is that there is no simple strategy that will dramatically affect levels of urban congestion.
The design of packages of measures is the key to success in travel reduction. Evidence suggests that a combination of constraints on vehicle use and provision of attractive alternative modes work well. In addition, land-use planning measures are needed to constrain the decentralisation of population and economic activity to locations beyond the area in which the restrictive policies apply. Fuel taxes, vehicle taxes and road pricing need to be co-ordinated so that the right signals are sent to vehicle users in congested areas, while avoiding inefficiently high taxation in uncongested rural areas.
Within a policy framework that aims to reduce growth in road traffic, while maintaining private sector interest in the financing and management of road infrastructure projects, the public sector will need to develop new ways to pay for roads. Otherwise, would-be investors will be deterred by the sensitivity of income projections to new traffic reduction initiatives.