Ogilvie et al. BMC Public Health 2010, 10:703 http://www.biomedcentral.com/1471-2458/10/703 Page 4 of 13 Figure 1 Study area. © Crown Copyright 2009. An Ordnance Survey/EDINA supplied service. baseline data collection from the new participants in the corresponding period of 2010. Written informed consent was obtained from all participants. Intervention When the Cambridgeshire Guided Busway opens, it will be the longest of its kind in the world [35]. This major new piece of transport infrastructure will link towns and villages to the northwest of Cambridge with the Cam- bridge Science Park, the city centre and the Cambridge Biomedical Campus at the Addenbrooke’s Hospital site on the southern fringe of the city, a site that is said to gener- ate more traffic than any other in the East of England. Buses will run on a completely segregated track along most of the route, avoiding traffic congestion both on the A14 trunk road approaching Cambridge and between the railway station and the hospital (Figure 2, Figure 3). A new high-quality bidirectional off-road cycle route is also to be provided adjacent to the busway. The busway is central to the plans for the new town of Northstowe, which is planned to be built on a former military site adjacent to the route northwest of Cambridge. Like most infrastructural developments of this kind, the construction of the busway is not taking place in isolation and it cannot easily be regarded as a discrete intervention for the purposes of evaluation. Concurrent changes in the local built environment include a new housing development at Orchard Park adjacent to the route on the northwestern edge of the city [36]; the construction of a new access road and cycle route to the Cambridge Biomedical Campus from the southwest [37]; and other new infrastructure for cycling in and around Cambridge funded by the national Cycling Towns programme [38]. Furthermore, the completion and opening of the busway has been repeatedly delayed. Its implementation is therefore best regarded as a phased process. New buses have been operating on the road network, and parts of the cycle route have been opened in stages, the majority of the northern section having been open for use by pedestrians and cyclists since October 2009. The full opening of the busway is now not expected to take place until early 2011, nearly two years later than originally announced [35].