The effect of changes in light level on the numbers of cyclists

Cycling has a range of benefits and should be encouraged, but darkness may put people off from cycling due to reductions in visibility, road safety and personal security. We summarise previous work that consistently demonstrates how darkness reduces the number of people cycling after dark, after accounting for confounding factors such as time of day and seasonal variations in weather. We extend this previous work by analysing cyclist counts in Norway, a country at a higher latitude than those examined previously. An effect of darkness on cycling rates was found but this effect was smaller than that found in previous work, suggesting certain unknown factors may be important in mediating the impact of darkness on cycling rates. One factor that is known to mediate the effect is road lighting. Previous findings indicate that increased illuminance can offset the reductions in cyclists caused by darkness and also that there may be an optimal illuminance after which no further benefits may be achieved.