Regional road network. Data from the Swedish National Road Network. No heavy road means that no registered road was available in the database, but local traffic could exist. The traffic intensity categories of (0–1, 2–5, 6–10, >10) cars/min corresponds to daily mean traffic counts of (0–2880, 2880–8640, 8640–14400, >14400) cars/day.
Lindgren et al. International Journal of Health Geographics 2009 8:2 doi:10.1186/1476-072X-8-2