In a study conducted by the Dutch Ministry of Infrastructure and Environment, the accident figures from a number of cities were compared with the number of cyclists that rode without lights in those cities. The conclusion was that the (bicycle-to-motor-vehicle) accident risk for cyclists riding in the dark falls by about 17% when their bicycle has working front and rear lights. According to the Ministry, another recent study in Denmark shows the same sort of results.
The SWOV has now issued a fact sheet stating that this and other studies are not yet conclusive about the effect of bicycle lighting on the safety of cyclists riding in the dark. The research institute points to a study conducted in Great Britain in which the absence of bicycle lighting in dark or poor visibility conditions was deemed to be a “contributory factor” in 5% of all fatal bicycle accidents and in 4% of all seriously injured cyclists, but SWOV thinks that those results cannot portray the Dutch situation.
Cycling in the dark is indeed more dangerous than cycling by day. This applies, at any rate, to all accidents between cyclists and motor vehicles and even more so for the 18-24 age group. According to the SWOV, alcohol may play a role. Data from the National Medical Archives points out that roughly 30% of cyclists who were seriously injured in accidents not involving a motor vehicle, had alcohol in their blood. This percentage has increased during the last 15 years.