Many cities are increasingly trying to 'manage' transport to support a range of policy objectives, such as reducing environmental damage and congestion and encouraging modal shift. Physical measures include restriction of road space for private cars, traffic calming, parking controls, priority for public transport, cyclists, and pedestrianisation. Such measures have been applied, often individually, in many cities - but their relative merits and the best ways of using them are not well understood.
OPIUM aimed to evaluate a range of physical measures for traffic management through their practical implementation in a number of cities (Gent, Heidelberg, Liverpool, Nantes, Patra and Utrecht), and make recommendations for the future development of urban transport policies.
Schemes to restrict road space and parking space for private cars proved very successful in terms of their impact on travel behaviour and consequent environmental benefits. The main difficulty lay in opposition from shopkeepers, although residents and visitors were generally supportive.
Traffic calming reduced overall traffic speeds and noise at a local level. This was perceived to benefit vulnerable users and could reinforce measures to promote modal shift. However, there may be negative effects on vehicle emissions unless overall car use is restricted.
Parking management and guidance appeared successful in reducing circulating traffic at a local level, and could influence modal split if implemented widely across a city. Parking measures were generally self-financing.
Public transport priority did not have a strong influence on modal split, but improved the speed and reliability of bus services. Greater modal shift might have been achieved if priority measures were implemented more extensively or integrated with traffic restrictions and improvements to bus services.
Measures to favour cyclists and pedestrians had only limited effect on modal shift when used in isolation, but were perceived by users to improve safety.
The greatest environmental benefits were achieved where road space was closed to private cars or where traffic volumes were reduced. Park-and-ride and parking schemes were successful in this respect. However, measures that led to slower speeds and increased journey times, such as traffic calming and bus priority, resulted in an increase in pollutant emissions.
All the schemes within OPIUM had a positive cost-benefit ratio, with payback periods of ten years or less.
OPIUM concluded that public consultation needs to play an increasingly important role in the development of traffic management measures. It is needed to gauge public opinion during scheme design and implementation, to educate the public about the likely benefits, and to take account of the needs and concerns of specific stakeholder groups such as shopkeepers. Stakeholder opposition proved to be the main hurdle to the schemes tested by OPIUM.
Individual measures can yield benefits in their own right, even if used only locally, but their deployment as part of an integrated strategy has the potential to yield significantly greater benefits. In particular, public transport priority and bicycle measures are increasingly effective at larger scale.
OPIUM recommended a number of areas for further research, particularly in relation to public consultation and the evaluation of user needs.