February 29, 2008

ROADWARE

Automatic Road Analyzer (ARAN) vans are among the tools currently used by MTO to inspect road smoothness at the network level. A new standard will apply the International Roughness Index at the contract level as well.

Standards

MTO considers applying international quality index

Road roughness examined by varying methods

PETER KENTER

correspondent

TORONTO

The International Roughness Index (IRI) has been used by the Ontario Ministry of Transportation (MTO) for more than a decade as an internal benchmark for the smoothness of the province’s road surfaces.

An initiative by the Ministry could soon see the same standard applied to roads at the contract level.

In Ontario, pavement profiles are currently measured at the contract level according to The Profile Index (PI) using a California Profilograph, the familiar “rolling straightedge.”

“Although they’re still widely used in about 70 per cent of U.S. states, the California Profilographs are becoming outdated,” says Sandy Brown, technical director of the Ontario Hot Mix Producers Association (OHMPA). The device can only measure smoothness in one wheel-path at a time, at about three to five kilometres per hour, and exposes operators to traffic in adjacent lanes.

“It’s also harder to get replacement parts, and updates for computers are currently on hold,” he says.

IRI, on the other hand, pays particular attention to surface irregularities that contribute to a rough ride for vehicle occupants and can be measured using several tools, including the rod and level and dipstick.

The quickest method of measuring IRI, however, is the inertial profiler, a laser sensor-equipped vehicle that can include modified golf carts, retrofitted trucks and dedicated vehicles, such as MTO’s Automatic Road Analyzer (ARAN) vans. Inertial profilers can measure smoothness at speeds in excess of 20 kilometres per hour to near highway speeds.

Another advantage of using inertial profilers is that they require no proprietary software to interpret smoothness data. ProVal, a computer program developed by the U.S. Federal Highway Administration, is used to convert raw data into the same values, regardless of source.

A joint committee of MTO and OHMPA will be comparing the technical details of smoothness measurements using California Profilographs and those derived using inertial profilers to find a reasonable measurement by which contractor roadwork can be measured. MTO and the Ontario Road Builders Association will then work together to resolve any contract issues.

“Asphalt pavements have become progressively smoother over the past 10 years,” says Brown.

“There’s not a need to create an even smoother pavement at this time, so we’re conducting side by side trials this fall to find a revenue neutral point between the California Profilographs and the inertial profilers.”

Brown notes that 15 years ago consultants owned three or four California Profilographs to help Ontario contractors determine road smoothness. Today, the province’s contractors own about 30 of the devices themselves.

“I imagine contractors will eventually want to do the same thing with inertial profilers,” says Brown. “But it’s going to take some time to ramp up to that.

Currently, there are only two or three units in the province. The biggest problem will be getting equipment calibrated, getting technicians trained, getting everyone to measure properly and learning the technical requirements of the device.”

MTO has no hard and fast plans as to when the switch to IRI will occur.

“I think the MTO would be happy if it all happened as quickly as possible,” says Brown. “But I don’t think contractors want to spend $40,000 to $70,000 per unit until the kinks are worked out in side-by-side trials this fall.”

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