Road lighting for safety: a forward-looking, safe system-based review

Road lighting for traffic is primarily a safety measure. The literature generally ascribes some level of crash reduction to improved road lighting but papers seldom specify whether lighting existed before the change, or its level where it did exist. One is left to assume that, at least after the change, the lighting satisfied the standards of the appropriate road controlling authority. These standards vary considerably worldwide and are based on practitioner consensus. This is because few data have been available to link safety to the actual standard of lighting. This means that any dose-response relationship lacks clarity. Locally, this situation is compounded in that both Australia and New Zealand have little history of measuring the reflective properties of pavements. Both countries' standards are based on measurements carried out decades ago. With this in mind the New Zealand Transport Agency contracted Opus Central Laboratories to carry out on-site measurements of the reflective properties of a sample of New Zealand pavements. The results indicate that New Zealand pavements, lit for safety purposes, are considerably less reflective, and thus the roads are less safe than previously thought. The literature indicates that this may be more than just a localised problem for New Zealand. Using a forward looking approach, this paper discusses the safety aspects of lighting within a safe system framework, and draws conclusions in the light of the literature and the aforementioned work carried out in New Zealand.