• A total of 21 studies met the inclusion criteria, all of which were observational studies. Eleven studies identified objectively measured environmental factors with a significant positive association with cycling.
• The environmental factors identified as being positively associated with cycling included presence of dedicated cycle routes or paths, separation of cycling from other traffic, high population density, short trip distance, proximity of a cycle path or green space and for children projects promoting ‘safe routes to school’.
• Negative environmental factors were perceived and objective traffic danger, long trip distance, steep inclines and distance from cycle paths.
• Of the seven studies which focused primarily on the impact of cycle routes, four demonstrated a statistically significant positive association.
• Although the study identified environmental factors with positive and negative associations with cycling behavior, many other types of environmental policies and interventions have yet to be rigorously evaluated.
• Policies promoting cycle lane construction appear promising but the socio-demographic distribution of their effects on physical activity is unclear. The wider impact of active transport policies on health and inequalities across Europe must be explored.

Fraser, Simon, Lock, Karen. "Cycling for transport and public health: a systematic review of the effect of the environment on cycling." The European Journal of Public Health. (2010)