The Effect of Darkness on the Number of Cyclists

Cycling remains a marginal mode of transportation in many countries despite its known benefits and the efforts made by those countries to promote it. Darkness may be one barrier to cycling, as without sufficient light cyclists may experience a reduced sense of safety because it is more difficult to see obstacles in their path and to be seen by other road users like motorists to avoid collisions. The main aim of this thesis is to investigate the effect of darkness on cycling rates.

Previous studies have used a comparison of cyclist counts in case hours (that change between daylight and darkness) and control hours (that remain in the same ambient light condition) to assess the effect of darkness on cycling. These studies tended to use only one to two case and control hour combinations in their analysis, when up to 88 other combinations are possible across their datasets. This thesis shows that the choice of case and control hours significantly impacts the measured effect of darkness. An alternative method is therefore proposed to combine all possible case and control hour combinations into a single measure of the effect of darkness on cycling.

The improved method is then applied to cycling data from 15 cities around the world to investigate the effect of darkness on their cyclists. The findings from this analysis confirm a reduction in cyclist numbers after dark, with the size of this effect varying across cities. When exploring this variance at a city scale, the effect of darkness tended to decrease in cities higher in latitude and stronger in cycling culture; when exploring this variance at the scale of cycling sites within the city, the effect of darkness tended to decrease in sites dominated by utilitarian cycling and closer to the city centre.