Visibility aids for pedestrians and cyclists: a systematic review of randomised controlled trials

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Abstract

This study aims to quantify the effect of visibility aids on the occurrence of pedestrian and cyclist–motor vehicle collisions and injuries, and drivers’ responses in detection and recognition. Trial reports were systematically reviewed according to predefined eligibility criteria, including randomised controlled trials or controlled before-and-after trials comparing visibility aids and no visibility aids, and of different visibility aids on pedestrian and cyclist safety, and drivers’ responses in detection and recognition. This included trials in which the order of interventions was randomised, or balanced using a Latin square design. Two reviewers independently assessed validity of trials and abstracted data. The main outcome measures were pedestrian and cyclist–motor vehicle collisions and injuries, and drivers’/observers’ responses in the detection and recognition time, distance and frequency. No trials which assessed the effect of visibility aids on pedestrian and cyclist–motor vehicle collisions and injuries were identified. Twelve trials examined the effectiveness of daytime visibility aids and 25 trials on night time visibility aids, including 882 participants. Drivers’ and observers’ detection and recognition improved with visibility aids. For daytime, fluorescent materials in yellow, red and orange colours enhanced detection and recognition. ‘Biomotion’ markings enhanced recognition. Substantial heterogeneity between the trials limits the possibility for meta-analysis. Visibility aids have the potential to improve detection and recognition and would merit further development to gain public acceptance. However, the impact of visibility aids on pedestrian and cyclist safety is unknown and needs to be determined.

Introduction

Road traffic crashes account for over a million deaths and some 10 million permanent disabilities a year worldwide (Murray and Lopez, 1996). Nearly three-quarters of road deaths occur in low and middle-income countries (Odero et al., 1997), predominantly as a result of cycle and pedestrian injuries. In 2000, there were 42,033 pedestrian and 20,612 bicyclist casualties in the UK (DETR, 2001).

One of the basic driver errors responsible for collisions is the late detection of other road users (Rumar, 1990). Pedestrian casualties are over-represented at night, partly due to reduced visibility (Owens and Sivak, 1993). Night time cycling is two–five times more dangerous than cycling in daylight and 40% of the bicyclists fatalities occur during the hours of darkness (Jaermark et al., 1991).

Walking and cycling are essential modes of travel for many in low and middle-income countries, and are also promoted for their environmental, economic and health benefit. Visibility aids such as reflective garments enhance the conspicuity of the pedestrians and cyclists, thus attracting the driver’s attention to their presence. The efficiency of visibility aids depend on whether they can visually alert the drivers in time to avoid a collision. Many factors affect conspicuity, including object contrast, size, movement, illumination, background ‘clutter’ and road condition, also the cognitive process of the driver and his/her responses in detection and recognition. To assess the effect of visibility aids on pedestrian and cyclist safety and on drivers’ responses in detection and recognition, we conducted a systematic review of randomised controlled trials of visibility aids.

Section snippets

Identification and selection of trials

We identified relevant randomised controlled trials and controlled before-and-after trials from 1963 to May 2001 by computerised searches of the Cochrane Controlled Trials Register, the specialised register of the Cochrane Injuries Group, MEDLINE, TRANSPORT, National Research Register and PsycINFO. A randomised controlled trial was defined as a trial in which the subjects were assigned prospectively to one of the two (or more) interventions by random allocation or some quasi-random method of

Results

Our search strategy found 1991 potentially eligible reports (Fig. 1). We did not find any trials quantifying the effect of visibility aids on the occurrence of pedestrian and cyclist–motor vehicle collisions and injuries. However, we identified 29 papers reporting 37 trials which assessed the effect of visibility aids on drivers’ and observers’ responses in detection and recognition, involving 882 participants aged between 17 and 77 years. These 37 trials were conducted in seven countries and

Discussion

We did not find any randomised controlled trials or controlled before-and-after trials which compared the effect of visibility aids on the occurrence of pedestrian and cyclist–motor vehicle collision. The effect of visibility aids on pedestrian and cyclist safety therefore remains unknown. However, results of the trials reviewed do suggest that visibility aids influence drivers’ reaction, detection and recognition. For daytime, fluorescent materials in yellow, red and orange colours improved

Acknowledgements

A full version of this review (Kwan and Mapstone, 2002) has been published in the Cochrane Library, where it will be regularly updated to take account of new data and comments. Contributors: Irene Kwan and James Mapstone independently screened the electronic search results, applied inclusion criteria and extracted data. Irene Kwan developed the protocol, contacted authors, entered data into RevMan and wrote the review. James Mapstone commented on the review and helped to write the review. We

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