Good Thinking

Impact-absorbing traffic light poles could save lives

Impact-absorbing traffic light...
Testing shows how one of the prototype poles absorbs impact energy by tilting to one side when hit by a car, instead of snapping off and possibly hitting bystanders
Testing shows how one of the prototype poles absorbs impact energy by tilting to one side when hit by a car, instead of snapping off and possibly hitting bystanders
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Testing shows how one of the prototype poles absorbs impact energy by tilting to one side when hit by a car, instead of snapping off and possibly hitting bystanders
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Testing shows how one of the prototype poles absorbs impact energy by tilting to one side when hit by a car, instead of snapping off and possibly hitting bystanders

When a car crashes into a roadside object at an intersection, chances are pretty high that object will be a traffic light pole. If it's a new energy-absorbing pole, however, the likelihood of injury or even death may be significantly reduced.

Traditional street light poles are relatively rigid and unyielding, so collisions with them can be quite nasty for the driver. Additionally, if a pole does snap off its base when smashed into hard enough, it may hit pedestrians standing nearby. Plus, of course, the entire pole and the damaged lights then have to be replaced.

"Recent statistics show that in Australia, traffic light collisions cost $18.5 million a year in fatalities, $53.7 million for injuries and up to $16 million annually to repair, install and maintain traffic lights," says the University of South Australia's Dr. Mohammad Uddin.

With such stats in mind, he and the university have partnered with Australian company Impact Absorbing Systems to create street light poles that absorb kinetic energy. These poles will incorporate a system that is already utilized in the company's energy-absorbing steel bollards.

In that system, the bottom section of each bollard sits inside a cavity within the bollard's concrete foundation. That cavity is cone-shaped – it's the same diameter as the bollard at the bottom, but wider at the top, forming a gap between the bollard and the concrete. That gap is filled by a polyurethane foam cartridge that goes around the cylindrical bollard, keeping it standing up straight … until it's run into by a car, that is.

When that happens, the cartridge compresses as it absorbs the impact energy, allowing the bollard to tilt to one side without snapping. The company claims that the result is less of a sudden impact to the car and driver, and less chance of damage to the bollard.

That same technology is now being scaled up for use on the traffic light poles. It is hoped that they will be ready for use within a year.

"We expect these new energy-absorbing traffic lights (EATL) will be the standard model going forward, not only for new installations but also to gradually replace existing lights," says Uddin.

Sources: University of South Australia, Impact Absorbing Systems

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paul314
Breakaway poles for other kinds of roadside objects (signs, power/communications lines) have been around for decades; good to see an alternative for light poles. (One of the problems, of course, is that all of these things are designed to last as long as possible, so it may be generations before all of the old unforgiving versions are replaced)