This paper draws on two projects: a pan-European meta-study and a before-and-after evaluation of the partial pedestrianisation of Brighton’s Old Town. The EVIDENCE Project reviewed and evaluated academic literature and other international sources on the costs and benefits of measures which may be included in a Sustainable Urban Mobility Plan. Some of those measures relate to pedestrianisation, road closures and road capacity reduction. The findings provide some limited evidence of economic and other benefits from these measures; they suggest that road closures reduce overall traffic levels but there remain significant gaps in the knowledge base. There has been very little published literature on pedestrianisation in Britain in the past 20 years. The Brighton case study began with a baseline survey and traffic count in 2013, which found a high level of public support for the planned pedestrianisation. Over two thirds of visitors arrived using sustainable modes; less than 3% had parked in the immediate area. The post-implementation study found modest traffic reduction within the Old Town and an increase in cycling to the Old Town during the week. The original plans encountered political opposition and planning obstacles; they were implemented in a reduced form. Many of the public surveyed would prefer the Council to go further. What began as a technical study has broadened into a study of process, drawing on interviews with supporters, opponents and councillors from opposing parties. This paper and presentation will tell the story of how politics and public perceptions can thwart, support or deflect plans to improve the quality of the urban environment.