What aspects of traffic intensity most influence cycling mode choice? A study of commuting in Surrey, UK

Motorized traffic discourages cycling, but the relative influence of different aspects of traffic intensity on commuter cycling rates is under-examined. This paper investigates these influences. It employs census data that describes the origins, destinations and mode choices of commuters travelling 2-5km in Surrey, UK (n = 172,665) and derives the shortest cycling route available for each commuter. Observed and modelled transport data is used to characterize traffic on these routes. The relationship between route-level traffic characteristics and the probability a commuter chooses to cycle is then examined using logit models for all commuters, males (42%) and females (58%). Two models consider the following aspects of traffic intensity both along the cycling route and crossing (intersecting) the route at junctions: speed; volume; and the proportion of heavy goods vehicles. The models also consider the influence of separated cycle paths, hilliness and distance. Above-median traffic speeds (>29km/h) along a commuting route is shown to have the greatest negative influence on cycling propensity, followed by above-median traffic volumes (>273 veh/h) and above-median speeds (in combination) crossing the commuting route. Cycle paths have a positive influence on cycling propensity, whereas the proportion of heavy goods vehicles does not show a significant relationship. The results imply that careful management of traffic at the route scale or the provision of separated cycle paths could encourage cycling on key commuting corridors. The relative influence of different characteristics could also identify the optimal locations for intervention. Findings support 30km/h (20mph) speed limits as a mechanism for encouraging cycling