The health impact of free bus travel for young people in London : protocol for an observational study

The extension, in September 2005, of free bus and tram travel in London to people 12-16 years of age and, in September 2006, to people under 18 years is likely to have had a range of impacts with implications for public health. The ‘On the Buses’ project aims to evaluate these impacts using a mixed method quasi-experimental design. This paper describes the protocol for the analyses of quantitative data for the study.