Arguments about transport policy often focus on particular solutions :- should a bypass be built? should a bus lane be provided? should railways be privatised? should car use be curbed? This approach has two important weaknesses. Firstly transport policy serves a number of purposes, and a solution which is right for one may not be right for others; reducing car use may protect the environment, but it could easily cause problems for business. Secondly, transport is a complex system, and changes to one mode of transport will have knock-on effects on others; reducing car use will increase the level of public transport required. This Knowledgebase is designed to assess the contribution of each possible "solution" on its own and as part of a wider transport strategy. In doing so, it is helpful to adopt a logical approach.

The above figure presents a structure for strategy formulation, based on the principles of systems analysis, in which objectives are the starting point. They are used initially to identify problems, both now and in the future, as indications that the objectives are not being met. Possible solutions are then identified, not as desirable measures in their own right, but as ways of overcoming the problems which have been identified. The potential solutions are then compared, often by means of a predictive model of the transport system, by appraising them against the objectives which they are designed to meet. As measures are implemented, their impact is assessed, through before and after studies, again in terms of achievement against objectives. On a regular basis, too, conditions are monitored and the current conditions and problems reassessed, in terms of the overall objectives.

This process may seem somewhat idealised and remote from standard practice, but it has several virtues. First, it offers a logical basis for proposing solutions, and also for assessing any proposals offered by others. If the answer to the question "what problems would this solution solve?" is unconvincing, the solution is probably not worth considering. Secondly, it ensures that the appraisal of alternatives is conducted in a logical, consistent and comprehensive way against the full set of objectives. Thirdly, assessing the performance of the implemented measures improves the ability to judge the potential of similar measures elsewhere, and to predict their impact. Fourthly, regular monitoring provides a means of checking not just on the scale of current problems, but also, through attitude surveys, on the perception of those problems. In this way the specification of objectives, and of their relative importance, can be modified to reflect changing attitudes and concerns. The last two of these are represented by the feedback loops above.

The practice of transport planning can be very different. Decision-makers may have a very clear view of what they want to do, and need no detailed, objective-based analysis to support their decisions. Conversely, there may be so many different organisations involved in decisions on transport that the emphasis is on consultation and consensus rather than detailed analysis. Even where it is clear that a given policy instrument is appropriate, based on experience elsewhere, there may be legal, financial or political reasons for not introducing it. And even when a particular policy instrument is introduced, there is often no budget, and little enthusiasm, for detailed appraisal of its impacts. As a result, we miss many opportunities to learn more about the complexities of urban transport systems, and the contributions which different types of policy instrument can make.

Level 1 of the Knowledgebase sets the scene for the assessment of individual policy instruments in Level 2, and of packages of measures in Level 3. Section 2 considers in more detail these approaches to decision-making; it outlines in turn:
· approaches based on vision, planning and consensus-building;
· objective-led and problem-led plans;
· the distribution of responsibilities for transport;
· the wider group of interests which might be expected to participate in decisions;
· the time horizons over which strategies are developed; and
· the external factors which might influence strategy performance.

Sections 3 to 7 then consider in turn:
· the objectives which might be set for transport policy, and the problems which arise when objectives are not being met, the indicators which can be used in assessing the scale of problems and performance against these objectives, and the potential for setting performance targets;
· the past trends which will have contributed to current transport conditions, the external factors which might influence future performance, and the ways in which these can be assessed using scenario planning;
· the range of land use and transport policy instruments available, the ways in which their performance can be assessed, and the potential for combining these policy instruments into an overall strategy;
· the barriers to implementing these policy instruments, and the ways in which these can be overcome; and
· the approaches which might be adopted in formulating an overall strategy.

The adjacent figure illustrates conceptually how these strands interact in strategy formulation. Section 5 provides the list of policy instruments which are considered in detail in Level 2. Section 3 specifies the objectives and problems which are used in assessing the contribution of each of these policy instruments in Level 2. Section 6 lists the barriers which are considered for each policy instrument in Level 2. Section 7 provides an introduction to Level 3.

The concepts throughout Level 1 have been tested in detail in a major study of decision-making in transport in Europe (May, Matthews and Jarvi-Nykanen, 2001). A total of 54 cities from 17 countries responded to a detailed questionnaire on the approaches which they adopted, and tables are provided indicating the responses obtained. Where relevant, distinctions are made between different areas of Europe and different sizes of city.