Here comes the knuckler

Just when you thought you knew all the noise solutions, AstroTurf makes an appearance

Asphalt Paving Article June 20, 2005
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Apparently I don’t pitch well on AstroTurf.
Back in February I wrote a column (see I hear to tell you, p 5) tossing out solutions for pavement noise. I thought I had three solid pitches: sound walls, porous friction courses and longitudinal tining. I’m told there is a fourth, and it may come at you like a knuckle ball. I’m really not sure where this pitch is going to go. As far as I know, it’s a brand-new solution. But just to make my quieter pavement repertoire complete, I thought I would loosen up my typing fingers and give it a whirl.

The state of Minnesota is now using dense, wiry, plastic grass—AstroTurf—over fresh concrete to provide skid resistance at a quieter noise level. The Minneapolis-St. Paul area has already put this technique in use on a couple of road projects: the widening and reconstruction of I-694 and Highway 100.

The Minnesota Department of Transportation (MnDOT) has been pulled every which way on the quieter pavement topic. Concrete has been an agency favorite since the dawn of the interstate era. But when the Federal Highway Administration began requiring tines to improve traction and water drainage in the late 1970s noise issues made the pavement an easy target. Complaints from the public were starting to pile up like a bad pitcher’s earned-run average. The uproar peaked in the 1990s, when residents of Bryn Mawr, a suburb of Minneapolis, insisted on an asphalt topping for the construction of I-394. MnDOT, however, was determined to give concrete a chance anyway and gave the material the go-ahead for the project. Shortly after construction commenced homeowners once again began chanting for a noise reliever, which forced the state legislature to apply an asphalt surface.

Some lawmakers were now ready to cut concrete from the roster altogether, but MnDOT was determined to make the paving process work and called on pavement research engineer David Rettner to pour in some study hours to come up with an answer. Minnesota actually turned to AstroTurf years ago to create the right surface texture on its low-volume roads. The process, however, wasn’t approved by FHWA. MnDOT insisted on doing all the legwork necessary to approve AstroTurf surface texturing on all roads and in 1999 was able to convince its federal boss that it was safe, logical and effective to use. The texture actually replaces the noisy grooves, which is something not every state has been able to perfect. MnDOT now has it down to a science.

In general metropolitan pavement hasn’t received enough attention. According to the latest urban pavement condition study by TRIP, approximately one in four miles of the nation’s metropolitan arteries, which includes interstates, freeways and critical local routes, are in substandard condition. The report, titled “Rough Ride Ahead: Metro Areas with the Roughest Rides and Strategies to Make Our Roads Smoother,” estimated that the average city motorist pays $400 annually in additional vehicle operating costs. Those with the highest percentage of poor roads are Kansas City (71%); San Jose (67%); St. Louis (66%); Los Angeles (64%); San Francisco-Oakland (60%); San Diego (58%); New Orleans (55%); Boston (49%); Sacramento (49%); and Oklahoma City (47%). Minneapolis-St. Paul wasn’t named to this year’s all-star team, which was led by Atlanta, Orlando and Phoenix. I’m sure the DOTs in those regions do an outstanding job keeping concrete and asphalt in shape, but they also do not have to contend with harsh winter weather.

Hearing what’s going on in Minneapolis-St. Paul is just another example of the impressive innovation and dedication the road- and bridge-building industry displays on a daily basis. It’s a shame that a report on the lack of maintenance is throwing a shadow over progress. Four pitches are great to have if you’re trying to sent noise pollution to the bench, but for the owners it’s all about how much money they’re able to spend. When it comes to highway funding, those in Congress appear to have a tight grip on the greenback. There are a lot of white knuckles, which is the last thing this industry needs.

About the author: 
Bill Wilson Editor in Chief [email protected]
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