The role of lighting in road traffic collisions

Abstract

The paper reports a study that examines how to determine if a road traffic collision took place in daylight or in the dark. An innovative method was developed, based on solar altitude, to establish cut-off points of daylight and darkness determined from a study of daylight availability in England, Scotland and Wales. This approach provides a rigorous method to differentiate daytime and night-time collisions. The criteria were used in a study of the collisions reported in the STATS19 data set for the weeks either side of the clock changes that are necessary between Greenwich Mean Time and British Summer Time. By comparing periods with the same clock time either side of the time change, using the aforementioned method, it was possible to isolate collisions within the same time period that during one week occurred in darkness and in the other week in daylight. The initial finding was that there are 19.3% more collisions in the dark periods and there is an even greater increase (31.7%) in pedestrian injuries.

A comparison of approaches for investigating the impact of ambient light on road traffic collisions

“…First, it may be the result of researcher degrees of freedom [Wicherts et al 2016], the apparently arbitrary decisions made during the analysis. Second, there are differences in definition of the before/after clock change periods, as can be seen by comparing Table 1 in the current article with Table 5 in Raynham et al [Raynham et al 2019].…”

“…The numbers of Case collisions that met the inclusion criteria are shown in Table 3. Two control periods were established, one in which it was dark for both weeks before and after clock change, and one in which it was daylight before and after the change, the same control periods as were used in previous work [Raynham et al 2019]. Table 4 shows the control periods and the numbers of RTCs that happened during each period.…”

“…This paper reports four analyses of RTCs carried out to compare the differences between methods of analysis. First, the analysis of Raynham et al 24 was repeated to test reproducibility, 25 the degree to which consistent results are reached when the same data are independently re-analysed. The Raynham et al method was then extended to establish an OR.…”

“…An assumption of insubstantial seasonal effects becomes less robust as the evaluation period increases.A recent study by Raynham et al[Raynham et al 2019] introduced a further development to the clock change method of investigating the effect of ambient light on RTCs. They considered RTCs in the seven day periods before and after clock change, and defined darkness according to civil twilight rather than sunset and sunrise.…”

Road lighting density and brightness linked with increased cycling rates after-dark

“…In previous work using odds ratios to assess effects of ambient light, daylight and darkness have effectively been treated as a binary distinction, with the light conditions either labelled as daylight or after-dark. In reality the transition between daylight and darkness, either on a specific day, or within the same hour at different times of the year, is gradual [39]. We explored the effect of this transition to darkness by calculating odds ratios for two stages of darkness: 1) Twilight, defined as the period between sunset and the end of civil twilight; and 2) Dark, defined as the period after civil twilight.…”