骑自行车有很多好处，应该受到鼓励，但由于能见度、道路安全和人身安全的降低，黑暗可能会让人们不骑自行车。我们总结了对观测数据的分析，以确认黑暗对自行车速度的负面影响。我们使用一种病例/对照方法来解释混杂因素，如一天中的时间和天气的季节性变化，从而证明黑暗对不同地点和国家的影响是一致的。不过，这种影响的大小各不相同，这表明某些未知因素可能在调节黑暗对自行车速度的影响方面很重要。一个已知的影响因素是道路照明。 我们表明，增加的照度可以抵消黑暗导致的骑车人减少，并且可能存在最佳照度，之后可能无法实现进一步的效益。

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 analyses of observational data to confirm the negative impact darkness has on cycling rates. Using a Case / Control method that accounts for confounding factors such as time of day and seasonal variations in weather, we demonstrate a consistent effect of darkness across different locations and countries. The size of this effect varies though, 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. We show 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.