Does darkness increase the risk of certain types of crime? A registered report protocol.

Evidence about the relationship between lighting and crime is mixed. Although a review of evidence found that improved road / street lighting was associated with reductions in crime, these reductions occurred in daylight as well as after dark, suggesting any effect was not due only to changes in visual conditions. One limitation of previous studies is that crime data are reported in aggregate and thus previous analyses were required to make simplifications concerning types of crimes or locations. We will overcome that by working with a UK police force to access records of individual crimes. We will use these data to determine whether the risk of crime at a specific time of day is greater after dark than during daylight. If no difference is found, this would suggest improvements to visual conditions after dark through lighting would have no effect. If however the risk of crime occurring after dark was greater than during daylight, quantifying this effect would provide a measure to assess the potential effectiveness of lighting in reducing crime risk after dark. We will use a case and control approach to analyse ten years of crime data. We will compare counts of crimes in 'case' hours, that are in daylight and darkness at different times of the year, and 'control' hours, that are in daylight throughout the year. From these counts we will calculate odds ratios as a measure of the effect of darkness on risk of crime, using these to answer three questions: 1) Is the risk of overall crime occurring greater after dark than during daylight? 2) Does the risk of crime occurring after dark vary depending on the category of crime? 3) Does the risk of crime occurring after dark vary depending on the geographical area?

Motorcycle safety after-dark: The factors associated with greater risk of road-traffic collisions.

The effect of ambient light level on road traffic collisions (RTCs) involving a motorcycle was investigated. Data were drawn from the STATS19 database of UK reported RTCs for the period 2005-2015. To isolate the effect of ambient light (daylight vs darkness) an odds ratio was used to compare RTCs at specific times of day in the weeks either side of the Spring and Autumn clock changes. This work extended previous studies by using a more precise method for distinguishing between RTCs in daylight and after dark, thus avoiding the ambiguity of twilight. Data for four-wheel motor vehicle (FWMV) RTCs were also investigated to provide a datum. As expected, the risk of an RTC occurring was significantly higher after dark compared to daylight for both motorcycles and FWMVs. Investigation of contextual factors suggests that risk after dark is significantly higher for motorcycles compared to FWMVs for RTCs with two-vehicles, on roads with low speed limits (≤30 mph), at T-junctions, and junctions controlled by a give way sign. These are the situations where visual aids for increasing conspicuity after dark have the greater potential for reducing motorcycle RTCs.

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

Cycling has a range of benefits as is recognised by national and international policies aiming to increase cycling rates. Darkness acts as a barrier to people cycling, with fewer people cycling after-dark when seasonal and time-of-day factors are accounted for. This paper explores whether road lighting can reduce the negative impact of darkness on cycling rates. Changes in cycling rates between daylight and after-dark were quantified for 48 locations in Birmingham, United Kingdom, by calculating an odds ratio. These odds ratios were compared against two measures of road lighting at each location: 1) Density of road lighting lanterns; 2) Relative brightness as estimated from night-time aerial images. Locations with no road lighting showed a significantly greater reduction in cycling after-dark compared with locations that had some lighting. A nonlinear relationship was found between relative brightness at a location at night and the reduction in cyclists after-dark. Small initial increases in brightness resulted in large reductions in the difference between cyclist numbers in daylight and after-dark, but this effect reached a plateau as brightness increased. These results suggest only a minimal amount of lighting can promote cycling after-dark, making it an attractive mode of transport year-round.

The effect of ambient light condition on road traffic collisions involving pedestrians on pedestrian crossings.

Previous research suggests darkness increases the risk of a collision involving a pedestrian and the severity of any injury suffered. Pedestrian crossings are intended to make it safer to cross the road, but it is not clear whether they are effective at doing this after-dark, compared with during daylight. Biannual clock changes resulting from transitions to and from daylight saving time were used to compare RTCs in the UK during daylight and darkness but at the same time of day, thus controlling for potential influences on RTC numbers not related to the ambient light condition. Odds ratios and regression discontinuity analysis suggested there was a significantly greater risk of a pedestrian RTC at a crossing after-dark than during daylight. Results also suggested the risk of an RTC after-dark was greater at a pedestrian crossing than at a location at least 50m away from a crossing. Whilst these results show the increased danger to pedestrians using a designated crossing after-dark, this increased risk is not due to a lack of lighting at these locations as 98% of RTCs at pedestrian crossings after-dark were lit by road lighting. This raises questions about the adequacy and effectiveness of the lighting used at pedestrian crossings.

Eye movement and pupil size constriction under discomfort glare.

PURPOSE: Involuntary physiological responses offer an alternative means to psychophysical procedures for objectively evaluating discomfort glare. This study examined eye movement and pupil size responses to glare discomfort using new approaches to analysis: relative pupil size and speed of eye movement. METHODS: Participants evaluated glare discomfort using the standard de Boer rating scale under various conditions manipulated to influence glare discomfort. Eye movement was recorded using an electro-oculogram (EOG), and pupil size was recorded using Tobii glasses. Ten young (mean age: 24.5 years old) and 10 senior (mean age: 61 years old) participants were recruited for this experiment. RESULTS: Subjective evaluation of glare discomfort was highly correlated with eye movement (multiple correlation coefficient [R(2)] of >0.94, P < 0.001) and pupil constriction (R(2) = 0.38, P < 0.001). Severe glare discomfort increased the speed of eye movement and caused larger pupil constriction. Larger variations of eye movement were found among seniors. CONCLUSIONS: The two physiological responses studied here to characterize discomfort glare under various lighting conditions had significant correlation with the subjective evaluation. The correlation between discomfort glare and physiological responses suggests an objective way to characterize and evaluate discomfort glare that may overcome the problems of conventional subjective evaluation. It also offers an explanation as to why long-term exposure to discomfort glare leads to visual fatigue and eyestrain.