Method for Road Lighting Audit and Safety Screening at Urban Intersections

Abstract

The review of recent research efforts in road lighting and safety shows an inconsistency in the methods to measure ambient road lighting. The importance of road lighting on improving night time safety is evident; however, the lack of actual illuminance field measurements results in a gap in the knowledge of whether installed road lighting provides adequate illuminance for clear visibility at night time or not. Previous studies considered the presence or absence of road lighting on safety without measuring actual illuminance of the road. This paper aims to propose a uniform methodology to perform a simple road lighting audit and safety screening that can be applied to any area.To perform the proposed audit, a photometric sensor, data logger and information on the city lighting standards, geo-referenced accident data and traffic flow data are needed. To collect field measurements, the data collectors cross each side of the intersection with the sensors starting and ending 15 m before and after the intersection. Information on land use, road type, location of light poles, location of trees and weather conditions is collected. Based on the collected data, average illuminance of each approach of an intersection as well as the average illuminance of the whole intersection and the uniformity ratio of the intersection was calculated. These results are then used to compare to the city lighting standard to check if the installed road lighting is performing adequately. If illuminance values of an intersection were below the standard specifications, the intersections were ranked as sub-standard.This methodology was then applied to a case study in Montréal, Québec, where 59 % of the selected sample intersections had sub-standard lighting. Statistical analysis showed that the number of night time accidents was correlated to traffic flow (or the ratio of minor to major flows) and the fact that the intersection average intersection illuminance did not meet the standard. The factors contributing to average illuminance were clear sky, hour of the night of the data collection, and presence of light poles and commercial lights. Nabavi Niaki, Saunier, Miranda-Moreno, Amador, Bruneau 2 INTRODUCTIONThe purpose of road lighting is to provide visibility, security and safety for all road users during the night (1-5). Once light poles are installed according to specification standards, they are assumed to provide adequate illumination to road users at night. However, lighting equipment might not be well maintained and there are hardly any follow-ups on the performance of lighting and its effect on safety. With time and resources constraints, there are usually few field measurements done by municipalities to check if lighting meets the specification standards. This is problematic because with the rapid change in traffic flow and land use, the amount of illumination needed for visibility also changes (6, 7). Road safety issues at night where lighting standards are not checked can be related to illumination deficiencies (1-4). Theref...

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