title: Changes in mode of travel to work: a natural experimental study of new transport infrastructure.
abstract: BACKGROUND
  New transport infrastructure may promote a shift towards active travel, thereby improving population health. The purpose of this study was to determine the effect of a major transport infrastructure project on commuters' mode of travel, trip frequency and distance travelled to work.
  
  
  METHODS
  Quasi-experimental analysis nested within a cohort study of 470 adults working in Cambridge, UK. The intervention consisted of the opening of a guided busway with a path for walking and cycling in 2011. Exposure to the intervention was defined as the negative of the square root of the shortest distance from home to busway. The outcome measures were changes in commute mode share and number of commute trips - both based on a seven-day travel-to-work record collected before (2009) and after (2012) the intervention - and change in objective commute distance. The mode share outcomes were changes in the proportions of trips (i) involving any active travel, (ii) involving any public transport, and (iii) made entirely by car. Separate multinomial regression models were estimated adjusting for commute and sociodemographic characteristics, residential settlement size and life events.
  
  
  RESULTS
  Proximity to the busway predicted an increased likelihood of a large (>30 %) increase in the share of commute trips involving any active travel (relative risk ratio [RRR] 1.80, 95 % CI 1.27, 2.55) and a large decrease in the share of trips made entirely by car (RRR 2.09, 95 % CI 1.35, 3.21), as well as a lower likelihood of a small (<30 %) reduction in the share of trips involving any active travel (RRR 0.47, 95 % CI 0.28, 0.81). It was not associated with changes in the share of commute trips involving any public transport, the number of commute trips, or commute distance.
  
  
  CONCLUSIONS
  The new infrastructure promoted an increase in the share of commuting trips involving active travel and a decrease in the share made entirely by car. Further analysis will show the extent to which the changes in commute mode share were translated into an increase in time spent in active commuting and consequent health gain.
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. eh480@medschl.cam.ac.uk.
authors.forename: Eva
authors.initials: E
authors.lastname: Heinen
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. jrp63@medschl.cam.ac.uk.
authors.forename: Jenna
authors.initials: J
authors.lastname: Panter
authors.affiliation: Department of Civil, Environmental and Geomatic Engineering, University College London, Gower Street, London, WC1E 6BT, UK. roger.mackett@ucl.ac.uk.
authors.forename: Roger
authors.initials: R
authors.lastname: Mackett
authors.affiliation: MRC Epidemiology Unit and UKCRC Centre for Diet and Activity Research (CEDAR), School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 285, Cambridge, CB2 0QQ, UK. dbo23@medschl.cam.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Ogilvie
mesh_terms: D000328:Adult; D001642:Bicycling; D015331:Cohort Studies; D004779:Environment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014186:Transportation; D014195:Travel; D006113:United Kingdom; D014505:Urban Population; D016138:Walking; D014937:Work; D055815:Young Adult