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Washington State expert questions lighting / safety links

There is no evidence that standard street lighting solutions lead to fewer crashes. And a lot of notions about lighting must be challenged. So says Dr John Milton, director of enterprise risk and safety management at the Washington State Department of Transportation (WSDOT) in the US, whose area covers seven million people, 11,200 kilometres of highways and 600,000 roadway lighting fixtures. John calls on people involved in street lighting to rethink their assumptions on links between lighting and safety.

By lumping together risk management and safety, he says, the department is able to look at things “a bit differently”.

WSDOT has a zero goal for serious or fatal crashes across the whole state. Frequently asked why the department would have such an ambitious goal, John says, “Because if I were to ask you how many fatal or serious crashes you are willing to accept for your family the answer would be zero. We can’t accept any less for the taxpayers of the State of Washington.”

For some time now, WSDOT has been going back to first principles in an attempt to pinpoint the link between street lighting and safety.

“We ask ourselves what we should focus on,” says John. “What does lighting address? That’s a simple question but not one that’s often answered. Where can you get greater benefit by installing LED or some other type of lighting? And what should we do to maximise our investment?” WSDOT is transitioning from a standards-based approach to using quantitative, substantive assessment in which it doesn’t just accept current lighting standards but challenges their underlying assumptions.

“I’m going to propose something to you today that most of you won’t like hearing – particularly in the lighting community – but we’re thinking about removing street lighting in certain places.”

He says while well-designed road lighting can reduce road crashes, poorly-designed lighting may increase accidents, for example by causing reflective glare that makes road markings invisible in wet weather conditions. Location of lighting is also important, he says. Lighting is likely to be of greater benefit on roads where there are lots of intersections and road access points, such as driveways, and to be of less benefit on stretches of double-lane highways without intersections. He says the old methodology of placing lights at standard spaces apart from each other may not have produced the greatest amount of return on investment.

“We’ve just been installing lights because the standards told us to do so.”

He says a lot of road lighting technology is now 40 years old and so is a lot of understanding of lighting and road crash potential. “New adaptive lighting technologies will enable us to optimise road lighting cost-effectively to create conditions that result in the fewest crashes, but we need to understand how to do that.”

Dr John Milton was speaking at the recent Road Lighting 2015 conference in Auckland organised by Strategic Lighting Partners.

This article was first published in the April 2015 issue of NZ Local Government Magazine.

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