Danish study shows how cyclists can reduce accident risks

Researchers at the Technical University of Denmark have analyzed police records to understand risk factors for cyclists. This showed that the probability of cyclist injury severity increases with:

  • Age under 10 years and over 40 years
  • Alcohol consumption: Drunk cyclists are 60% more likely to die when wearing a helmet and 457% more likely to die when not wearing a helmet.
  • Collision with a truck: This is 1,145% more likely to result in death than for other vehicles
  • Although cycle lanes do not reduce minor or severe accidents they do reduce fatalities
  • Slippery road surfaces increase the risk of fatalities by 48%
  • Road speeds over 50 kph increase the risk of severe and fatal accidents: speed limits of 50–60 km/h increase the risk of fatalities by 21–45% while for speed limits above 70 km/h this increased to 274–326%.

The database used contained 8,892 accident records reporting on the accident, persons involved and vehicles involved. 24% involved serious cyclist injuries and 1.7% cyclist fatalities.

The accident reports give the accident type, weekday, time of day, severity level, collision manner, road users, infrastructure characteristics, land use, and light and weather conditions. The associated person file gives demographics, alcohol or drug use, seat belt or helmet use, license validity, and injury severity of the persons involved. The vehicle file details the make and model, maneuver prior to the accident, weight, registration date, and collision point of the vehicles involved. Accidents which did not involve another person or vehicle were excluded since these types of accident are known to be very under-reported.

95% of accidents involved motorized vehicles and 71% occurred at intersections. Half of the accidents involved a cyclist riding straight and the driver turning, this is a clear warning that cyclists need to be highly defensive, anticipating drivers moving into their path. 81% of the accidents occurred during daylight and 75% on dry surfaces. Only 2% of cyclists and 1.4% of the people they collided with had blood alcohol over the legal limit. The statistical method of discrete choice modeling was used to identify which factors had a significant effect on injury severity.



Introduction: Denmark is one of the leading cycling nations, where cycling trips constitute a large share of the total trips, and cycling safety assumes a top priority position in the agenda of policy makers. The current study sheds light on the aggravating and mitigating factors associated with cyclist injury severity on Danish roads by examining a comprehensive set of accidents involving a cyclist and a collision partner between 2007 and 2011. Method: This study estimates a generalized ordered logit model of the severity of cyclist injuries because of its ability to accommodate the ordered-response nature of severity while relaxing the proportional odds assumption. Results: Model estimates show that cyclist fragility (children under 10 years old and elderly cyclists over 60 years of age) and cyclist intoxication are aggravating individual factors, while helmet use is a mitigating factor. Speed limits above 70-80 km/h, slippery road surface, and location of the crash on road sections are aggravating infrastructure factors, while the availability of cycling paths and dense urban development are mitigating factors. Heavy vehicle involvement and conflicts between cyclists going straight or turning left and other vehicles going straight are aggravating vehicle involvement factors. Practical applications: The results are discussed in the context of applied policies, engineering, and traffic management solutions for bicycle safety in Denmark


Aggravating and mitigating factors associated with cyclist injury severity in Denmark
Sigal Kaplan Konstantinos Vavatsoulas Carlo Giacomo Prato
Journal of safety research. , 2014, Vol.50, p.75-82

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