Single-bicycle crashes: An in-depth analysis of self-reported crashes and estimation of attributable hospital cost.

Cyclists' awareness of their risk of single-bicycle crashes is limited. Thus, knowledge of the most common contributory factors of single-bicycle crashes is required. Similarly, single-bicycle crashes and their costs to society are under-recognized by the public. The aim of this study was to conduct an analysis of single-bicycle crashes occurring in a cohort of cyclists in Denmark and supplement it with estimation of some attributable costs of single-bicycle crashes among all injured cyclists during one year treated in a hospital or emergency room in Denmark. We conducted a one-year follow-up of 6,793 active cyclists (mean age: 45.8 years) encountering 349 single-bicycle crashes (single-bicycle crash rate: 55 per 1,000 person-years). An in-depth analysis of the crashes suggested that daily winter road maintenance is crucial in colder climates and that the current cyclist infrastructure design gives rise to many single-bicycle crashes. Further analysis of the co-occurrence of the factors contributing to the crashes indicated that when the weather is warmer, the factors pertaining to the individual cyclist (and not the road authorities) dominate. The risk of sustaining a more severe injury (i.e. other than light bruises) once in a single-bicycle crash was 18 %. However, for cyclists above 50 years, this risk doubled compared with their younger counterparts, wholly due to a 4.7 times higher risk during the warm season. Among cyclists treated in hospital or emergency room, we estimated the attributable hospital cost of single-bicycle crashes at €1,701 and the attributable cost of municipality care at €417 in the first year after the injury (2019 prices). In cyclists aged 18-60 years and treated in hospital or emergency room, the estimated attributable risk of sickness benefit was 5.2 percentage points in the first year after the injury. We concluded that to increase cyclist safety, the road authorities should improve winter road maintenance and redesign cyclist infrastructure.