|Published February 14, 2005|
MINNEAPOLIS (AP) - Minnesota highway officials have found the key to creating a skid-resistant - and quiet - concrete highway: AstroTurf.
Officials drag the wiry, plastic grass over a highway's surface to rough it up and make it skid-resistant. The result is a different texture that is quieter to drive on than the grooves that had been previously placed in concrete.
The Federal Highway Administration said Minnesota is the first state to eliminate the old-fashioned grooves in favor of using AstroTurf.
The new texture appears to be just as safe as the grooves, said Curt Turgeon, pavement engineer for the Minnesota Department of Transportation.
"We have looked at accident data and we haven't been able to see any difference," he said.
Miles of quieter concrete lanes now are opening in the Twin Cities, including on new sections of Interstate 694 and Highway 100.
"It's a different hum, much better," said Bernice Swanberg of Golden Valley, who regularly drives the new stretch of Highway 100. She said when she recently drove over the old-fashioned grooved concrete on Interstate 35, "I thought 'What in the world was wrong with my car?"'
In the late 1970s, the Federal Highway Administration required grooves to be raked across concrete pavement to drain water and improve traction. However, tires passing over the grooves made such a loud noise that it became a public concern, said David Rettner, a former pavement research engineer for MnDOT.
With some legislators threatening to ban new concrete highways, MnDOT increased efforts to silence the whine.
"We had been building pavement with AstroTurf drag for lower-volume roads for a lot of years and it had always measured quiet, but it wasn't allowed by Federal Highway (on freeways) until we could demonstrate the skid resistance," Rettner said. "So we asked for permission to do a research project to see if we could make it quieter and make it skid-resistant."
The right texture was found after three years of testing. One formula offered good traction at first, but then wore down. On the next try, researchers made the surface so rough that it could withstand years of snow plowing, Rettner said.
"What we have out there now, if you were riding a bike and fell on it, it would rip all the meat off your bones. It is very skid resistant," said Rettner, who now is principal engineer for American Engineering Testing Inc. in St. Paul.
MnDOT won approval from the Federal Highway Administration to eliminate grooves on new concrete lanes in Minnesota. In new construction since 1999, Minnesota contractors have textured highways with AstroTurf or a similar technique employing stiff-bristled brushes.
Information from: Star Tribune, http://www.startribune.com© Copyright 2005 Star Tribune. All rights reserved.