LIMITATIONS ON THE OBJECTIVE OF ENERGY EFFICIENCY IN URBAN TRAFFIC MANAGEMENT

The objective of reducing fuel consumption in urban traffic must be considered in the context of an overall traffic system management approach. This paper emphasises the existence of conflicts among various traffic management objectives (safety, traffic performance, energy, air pollution, property access, intrusion into residential areas, etc) and among the needs of different road user groups (pedestrians, buses, cars, heavy vehicles, major and minor road traffic, etc). An elemental model of fuel consumption is described briefly, and its relevance to existing traffic modelling techniques is emphasised. The elemental model is then used as a basis for discussing the expected impacts of various short-term traffic management measures on traffic performance, fuel consumption, safety and other objectives. Theoretically, fuel consumption savings of about 5 to 10 per cent could be achieved from traffic control (at a local level) given the limitations imposed by other traffic system management objectives. However, considering time-dependent and location-specific characteristics of road traffic systems, it is concluded that, in order to achieve and maintain such levels of energy savings, continuous implementation of sophisticated traffic engineering techniques is required. Furthermore, the problem should be considered in the context of a wider transport system management approach which analyses relatively long term impacts on route choice, mode choice and travel demand levels. (Author/TRRL)