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Table 1 Details of exposure metrics, and descriptive statistics for home, school and route environments

From: Associations between BMI and home, school and route environmental exposures estimated using GPS and GIS: do we see evidence of selective daily mobility bias in children?

Variable Description - home/school neighbourhoods Description – routes Data source Descriptive statistics (Mean, SD)
Home School Modelled route Actual route
Access to facilities:        
Takeaway food outlets The inverse distance weighted sum of distance to all outlets/facilities within 6 km of home/school Number of outlets/facilities along the route, divided by route length A, B, C 3.29 (2.84) 4.40 (2.10) 0.33 (0.52) 0.19 (0.37)
All food outlets   6.38 (5.10) 8.44 (3.08) 0.64 (0.96) 0.37 (0.51)
Physical activity facilities   0.81 (0.62) 1.13 (0.34) 0.09 (0.16) 0.07 (0.10)
Green spacea Area of green space within neighbourhood as a percentage of neighbourhood area Area of green space along the route, divided by route length C, D 62.21 (15.15) 51.66 (11.48) 111.16 (25.50) 116.98 (191.84)
Road safety:        
Density of fatal road traffic accidents Number of fatal road traffic accidents in the neighbourhood 2002–2011, divided by total length of roads within the neighbourhood Number of fatal road traffic accidents along the route 2002–2011, per km of route length C, E 0.03 (0.07) 0.04 (0.05) 0.14 (0.34) 0.14 (0.20)
Proportion of roads that are major roads Length of major roads within the neighbourhood, divided by total length of roads within the neighbourhood Percentage of the route that is along a major road C 0.09 (0.13) 0.12 (0.09) 39.95 (33.53) 36.00 (24.57)
Street connectivity:        
Effective walkable area and route length ratio Effective walkable area: ratio of the area within an 800 m street network distance of a location to the total area within an 800 m Euclidean radius Route length ratio: ratio of length of route to the Euclidean distance between home and school C 0.18 (0.07) 0.25 (0.02) 1.16 (0.25) 2.78 (2.12)
Connected node ratio Ratio of junctions to junctions and cul-de-sacs n/a C 0.79 (0.11) 0.90 (0.06) n/a n/a
Land use mix:        
Herfindahl-Hirschmann Indexb The sum of squares of the percentage of each land use type in the neighbourhood The sum of squares of the percentage of each land use type along the route D 3716.44 (148.55) 3686.80 (730.00) 3564.09 (817.50) 3447.12 (703.70)
  1. Data sources: A = ReferenceUSA 2011 [53]; B = Geo-coded by trained researcher, 2011; C = Topologically Integrated Geographic Encoding and Referencing (TIGER) 2011 [54]; D = US National Land Cover Database (NLCD) 2006 [55]; E = National Highway Traffic Safety Administration (NHTSA) Fatality Analysis Reporting System (FARS) 2002–2011 [56].
  2. aUS NLCD land uses summed to represent ‘green space’: developed open space, woodland (combining deciduous forest, evergreen forest, mixed forest) and grassland.
  3. bNine different US NLCD land uses included: open water, developed open space, developed low-high intensity, barren land, woodland, scrubland, grassland, farmland and wetland.