Lighting Research

Abstract

This confirmatory study estimates the effect on Police Recorded Crimes (PRCs) of a relighting programme that installed nearly 80,000 white-light lamps, replacing predominantly orange ones, in the years 2005 to 2013, throughout the UK city of Leeds. Time series of weekly PRCs in all 107 Middle-layer Super Output Areas, while road lighting was being almost completely relit, were analysed using multilevel modelling. The background change in PRCs in each area, when and where no lighting was changed, was separated from that associated with when and where replacement white lamps were installed, by including a polynomial for the underlying time-trend. The key interest is how the replacement by new white lamps affects the rate of crime, from the start to the finish of the relighting. The results show that over the period, there was an estimated 2% rise in daylight adjusted darkness crime associated with relighting, 95% confidence interval (CI) (−3% to +7%). Similarly associated with relighting, (unadjusted) darkness crime showed a rise of 3%, 95% CI (−1% to +8%) and the round-the-clock measure of crime (the sum of darkness and daylight crime) gave an estimated rise of 3%, 95% CI (0% to +6%). Many checks were made, all giving consistent null results; that is, giving narrow confidence intervals around zero of only a few percent wide after relighting. Therefore, no evidence was found for an improvement (or detriment) in the city’s level of crime by relighting, contrary to the substantial reduction anticipated by the city council.

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Abstract

This article discusses the results and implications of large scale studies which have investigated the effect on road safety of changing road lighting. In particular it highlights the failure to detect any impact on road traffic collisions of changing to white light. It calls for more rigorous statistical work to be carried out before authorities make expensive changes in policy.

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Abstract

Large-scale installation of broad-spectrum (white) road lighting has been claimed to bring about a substantial reduction in road traffic collisions (RTCs). This confirmatory study estimates the effect on personal injury RTCs of a relighting programme that installed nearly 80,000 new white lamps, between the years 2005 and 2013, throughout the large UK city of Leeds. Time series of weekly RTC personal injury counts in 107 areas, within the city over nearly 9 years when its road lighting was almost completely relit, were analysed, using multilevel modelling. The background change in each area when and where no lighting was being changed was separated from that associated with when and where new replacement white lamps were installed by including a polynomial for the underlying time-trend. The key interest is how the installation of the new lamps affects the ratio of the rate of collisions occurring in darkness to those occurring in daylight. The measure sought is given by the daylight adjusted darkness collision rate ratio (CRR) for the specified amount of relighting, that is the factor by which the daylight adjusted collision rate changes by the specified change in lighting. The daylight adjusted darkness collision rate ratio (CRR) has a point estimate of 0.990 and a 95% confidence interval, CI (0.971, 1.010) for 100 replaced lamps; representing a range between a 3% reduction in the collision rate to a 1% increase. Using the series truncated at the end of 2011 that seems more trustworthy, gives a revised point estimate of 0.993 and a CI (0.971, 1.015). Both CIs include one, therefore no effect on road safety was detected. The CIs for any other number of lamps installed will also include one. Typically, the plausible range of road safety impact brought by the new white lamps for a typical area with 700 lamps, roughly spans 20% reduction to a 10% increase for the daylight adjusted darkness collision rate. No convincing evidence was found for an improvement (or detriment) in road safety by relighting with white lamps, despite the extensive, city-wide installation efforts and associated costs.

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Abstract

The paper of Jackett & Frith (2013), which purports to show considerable gains for road safety with increasing road luminance, is seriously flawed. It asserts that increasing the luminance on roads causes improvements in road safety. Its cross-sectional design fails to rule out major potential confounders. Using a longitudinal design would be a far superior approach. The paper exhibits poor statistical practice. The selection process for the relatively small sample of urban roads is unclear and the post hoc processing of the data is questionable. The analysis is seriously deficient, as variables which indicate detrimental effects of increased road lighting are removed from the modelling without proper justification and other variables are not included in the first analysis yet appear in the subsequent cosmetic analyses. The latter give an illusion of false certainty. The data collected, which would allow checking, is not published. The practice of the journal in which the paper appeared is seriously deficient in not allowing the publication of critical responses. Although being used to promote increased road lighting, the paper’s claim disagrees with results from better quality research.

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Abstract

Background A step change in the night environment is taking place, with the large-scale installation of bright, broad-spectrum road lighting such as white light-emitting diodes (LEDs). One justification for this is a reduction in road traffic collisions (RTCs). This study aimed to estimate the effect of new lighting on personal injury RTCs within a large UK city.

Methods We analysed a 9-year time series of weekly RTC personal injury counts in 132 areas of the city using multilevel modelling. The RTC rate over a full 24-hour period was the primary outcome; darkness and daylight RTC rates were secondary. The background change in RTC rate was separated from the change associated with the number of newly installed bright lamps by including a polynomial underlying time trend for the logarithm of the mean number of collisions per week for each area. The study was based on a rigorous, predesigned and archived protocol.

Results Within-area coefficients for the broad lighting effect were positive; as the number of bright lamps in an area increased, so did the RTC rate. The estimate for the increase in the within-area 24-hour RTC rate is 11% (95% CI 2% to 20%). The estimate of darkness-only RTCs is 16% (95% CI 2% to 32%). If the effect of lighting on darkness RTC rate is adjusted by that for daylight, one obtains 4% (95% CI −12% to +23%).

Conclusion No evidence was found for bright lamps leading to an improvement in road safety in any of the analyses. For this city, introducing brighter road lighting may have compromised safety rather than reducing harm.

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Abstract

Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin—the “hormone of darkness” and a key player in circadian regulation—can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01–0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower, wavelength-dependent intensities are implied by some studies and require rigorous testing in ecological contexts. In many studies, melatonin suppression occurs at the minimum light levels tested, and, in better-studied groups, melatonin suppression is reported to occur at lower light levels. We identify major research gaps and conclude that, for most groups, crucial information is lacking. No studies were identified for amphibians and reptiles and long-term impacts of low-level ALAN exposure are unknown. Given the high sensitivity of vertebrate melatonin production to ALAN and the paucity of available information, it is crucial to research impacts of ALAN further in order to inform effective mitigation strategies for human health and the wellbeing and fitness of vertebrates in natural ecosystems.

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Would a billion-dollar investment in improved street lighting make Australian roads safer at night? Paul Marchant finds the evidence wanting

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Abstract

This paper gives some background to claims of benefit from road lighting and why large beneficial claims may be suspect. It places this in the context of general concerns about the unreliability of claims in science using knowledge gained, particularly from investigations in the field of health-care.
It points to the need to plan, proceed and check science in unbiased and rigorous ways. It gives recommendations for more transparency, asks for clear protocols to be produced in advance, that clear reports are written which follow appropriate reporting guidelines and that the data is accessible.

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Abstract

Non-randomized trials can give a biased impression of the effectiveness of any intervention. We consider trials in which incidence rates are compared in two areas over two periods. Typically, one area receives an intervention, whereas the other does not. We outline and illustrate a method to estimate the bias in such trials under two different bivariate models. The illustrations use data in which no particular intervention is operating. The purpose is to illustrate the size of the bias that could be observed purely due to regression towards the mean (RTM). The illustrations show that the bias can be appreciably different from zero, and even when centred on zero, the variance of the bias can be large. We conclude that the results of non-randomized trials should be treated with caution, as interventions which show small effects could be explained as artefacts of RTM.

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Introduction

This paper gives some background to claims of benefit from road lighting and why large beneficial claims may be suspect. It places this in the context of general concerns about the unreliability of claims in science using knowledge gained, particularly from investigations in the field of health-care.
It points to the need to plan, proceed and check science in unbiased and rigorous ways. It gives recommendations for more transparency, asks for clear protocols to be produced in advance, that clear reports are written which follow appropriate reporting guidelines and that the data is accessible.

The full text is available here.

Introduction

Paul Marchant disputes the methods, and therefore the outcome, of an influential study that is the government’s rationale for increased street lighting.

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Abstract

When we look around an imperfect world, we feel an understandable impulse to improve matters. We may therefore decide to intervene by prescribing medical treatment or by introducing crime reduction measures. But how do we know that what we do is likely to work? In medicine the standard answer is to do a trial; not surprisingly the same is true in crime reduction. But, says Paul Marchant, the lessons learned from medical trials have not been implemented in the latter field.

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Abstract

This article discusses the important differences between evaluating area-based crime reduction interventions through comparison of areas, and evaluating treatment effectiveness by a classic randomised controlled trial (RCT). The differences must be respected in the analysis of data. Wrong results will be given for a comparative area- based crime reduction trial if it is thought of as an RCT. The problem with evaluations which compare areas, one with an intervention and one without, is that such studies are neither randomised nor controlled, and the crime events being counted are correlated rather than statistically independent. Wrongly using those methods which are appropriate for an RCT will give misleading results. Statistical uncertainties will tend to be large and poorly determined, and statistical biases problematic because of the lack of equivalence between areas at the outset. Crime studies need to be appropriately designed to avoid such problems if costly mistakes are to be avoided.

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Abstract

The major systematic review on street lighting and crime, Home Office Research Study 251, suggests that claims for the effectiveness of lighting against crime are justified. The review at first sight appears to be an appropriate statistical synthesis of all studies on street lighting and crime across the world. However on close examination, the statistical claims and methods are unfounded. In three cases examined there is a clear conflict between the evidence and the reviewers’ interpretation of this. One of the principal problems is easily seen. The time-series of the original data from the Bristol study shows no good evidence for the crime reduction benefit of lighting. However the review gives the result for the same data as being extremely statistically significant. It is suggested that such a difference between the newly lit and the control areas occurring purely by chance is less than one in a billion, but this is manifestly wrong. Two other component studies, Birmingham and Dudley, are examined.

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