Regional variations in pedal cyclist injuries in New Zealand: safety in numbers or risk in scarcity?

Objective: To assess regional variations in rates of traffic injuries to pedal cyclists resulting in death or hospital inpatient treatment, in relation to time spent cycling and time spent travelling in a car. Methods: Cycling injuries were identified from the Mortality Collection and the National Minimum Dataset. Time spent cycling and time spent travelling as a driver or passenger in a car/van/ute/SUV were computed from National Household Travel Surveys. There are 16 census regions in New Zealand, some of which were combined for this analysis to ensure an adequate sample size, resulting in eight regional groups. Analyses were undertaken for 1996–99 and 2003–07. Results: Injury rates, per million hours spent cycling, varied widely across regions (11 to 33 injuries during 1996–99 and 12 to 78 injuries during 2003–07). The injury rate increased with decreasing per capita time spent cycling. The rate also increased with increasing per capita time spent travelling in a car. There was an inverse association between the injury rate and the ratio of time spent cycling to time spent travelling in a car. The expected number of cycling injuries increased with increasing total time spent cycling but at a decreasing rate particularly after adjusting for total time spent travelling in a car. Conclusions: The findings indicate a 'risk in scarcity' effect for New Zealand cyclists such that risk profiles of cyclists are likely to deteriorate if fewer people use a bicycle and more use a car. Implications: Cooperative efforts to promote cycling and its safety and to restrict car use may reverse the risk in scarcity effect.