15 Sep 2017

Skid-resistant roads reduce crashes by 40%

3:39 pm on 15 September 2017

Advances in what we drive, such as driverless cars, are expected to slash the number of road deaths and serious injuries in years to come.

But improvements in the surfaces we drive on will also be crucial, the Transport Agency said.

Darren Newland and the SCRIM truck.

Darren Newland and the SCRIM truck. Photo: RNZ / Phil Pennington

The holy grail of road designs is the skid-less highway, as the injury crash rate is between 4.5 and 9 times higher on slippery roads than skid-resistant ones.

New Zealand is much farther along the track towards achieving that than many other countries, thanks in large part to two of the smartest trucks on the road, which employ laser wizardry so powerful they're the highway equivalent of Superman's stare.

"New Zealand are world leaders, they're right at the cutting edge of skid resistance, at least up there with Europe and probably even beyond," Darren Newland, who oversees the skid-test trucks for British company WDM, said.

"Head and shoulders [ahead] of the Americans in terms of continuous skid resistance monitoring."

WDM said skid-related fatalities have fallen nearly 40 percent since it began surveys of New Zealand highways for the Transport Agency in the mid 1990s.

Its latest high-tech trucks, which work only in this country, shoot 20 lasers at the road, detecting ruts and slumps, and measuring roughness and skid-resistance, all at a speed of up to 80km/h.

The Transport Agency crunches the data from the onboard computer dubbed 'The Tardus' and spots the blackspots.

Mark Owens of the Transport Agency.

Mark Owens of the NZ Transport Agency. Photo: RNZ / Phil Pennington

"A really good one would be at State Highway 2, just at the Petone underbridge, so we had regular crashes there with people sliding off," Mark Owen from the Transport Agency said.

"You've got a long straight and then a sharp bend. And by using this information we could say, yes, we've got a skid problem."

It helped pinpoint the best roadseal mix, in this case the priciest of them all, calcined bauxite, which is almost as hard as diamonds.

"The crashes just dropped right away. In the first two years [after re-sealing]... it was approximately two crashes at that site, whereas in the months before we'd had regular crashes there with people sliding off the road."

Among the tangible proof that highways are, as a whole, grippier than they once were, is that the smart trucks now go through several hundred skid-test tyres each summer, 10 times more than before.

"I truly believe that the work that we do ... actually saves lives out on the road," Mr Newland said.

WDM aims to expand the number of lasers under the truck from 20 to 3200, enough to scan each millimetre of the 3.2m-wide lane to detect every crack, and so help keep water out.

Meanwhile, the strength of the highways is being measured by another machine, the Traffic Speed Deflectometer, which is about halfway through a survey of all the highways that is due to wrap up late next year.