34: Evidence led policy or the art of the possible?

Dr Adrian Davis

Top line: Evidence-base guidance can be welcomed but also viewed as a threat to the existing world view. Separately, working out how to handle divergent evidence is as important a task as gathering more evidence. Transport planning is not immune to such tensions.

Public policy literature has been experiencing a new wave of interest in the issue of utilisation of research evidence for policy purposes. Moreover, the British government has committed itself to evidence-led policy and practice. Yet, barriers are personal, ideological, or heavy financial commitment to particular policies which make politicians resistant to negative findings. Public opinion may be so sympathetic or unsympathetic to particular policies or practices that evidence can play a part only at the margins. Cultural, organisational, and individual inertia and self-interest, fuel resistance to adapting policy and practice to research findings. Where evidence confirms existing prejudices, interests and decisions it is welcome. Where it challenges them, it is discreditable. The problem of selective publication of positive findings follows from the interest in demonstrating achievement, justifying policy and practice and leveraging further support, as against subjecting policy and practice to open critical scrutiny on the basis of evidence.1

More broadly, does more evidence lead to better policy or might it lead to incoherence between the implications of different sources of evidence? An apposite example is an analysis of New Zealands’s health priority setting in the 1990s for evidence-based policy.2  The authors note that few, if any people with an interest in good policy making would argue that there should be less evidence. However, arguments for evidence-based policy need to be located in the context of a much broader discussion regarding the significance and roles of evidence and knowledge in policy processes.

According to evidence-based policy advocates ‘… society appears to be guided more by politics than by science, and politics is more about the art of the possible or generally acceptable than in what is rationale or might work best’. One of the key assumptions that underpins the evidence-based policy movement is that the collection of more evidence will take policy actors closer to better, more rational policy decision-making. The authors concluded that in the case of New Zealand’s approaches to explicit health priority setting, efforts to gather more policy-relevant evidence, in themselves, are unlikely to lead to policy making that is more rational and less political.

Specifically regarding transport, despite the substantial volume of transport research, it is claimed that very little of this has been directed towards collecting and evaluating evidence to inform policy or towards assessing the effectiveness of policy into action.3 This has begun to change not least as predicting and providing more road space has been increasingly challenged and a consequent need to find alternatives to growing car use.


1 Tilley, N. 2005 Evaluation and evidence-(mis)led policy, Nottingham Trent University http://www.aes.asn.au/conferences/1999/Tilley%20Nick%20LS.pdf accessed 11th September 2009.
2 Tenbensel, T. 2004 Does more evidence lead to better policy? Policy Studies, 25(3): 187-207.
3 Terry, F. 2000 Transport: Beyond predict and provide, in Davies, T. (ed)What works? Evidence-based policy and practice in public services, Bristol: Policy Press.

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