The Drive: Indented markings don't harm pavement

Last summer, the Minnesota Department of Transportation (MnDOT) repaved the portion of I-394 between Hwy. 100 in Golden Valley and I-494 in Minnetonka, then painted new lane markings on the freshly poured asphalt.

Shortly after the smooth surface was laid down, MnDOT was back out on I-394 to groove the words "EXPRS" into the pavement at some entrances to the MnPass lane. The pavement markings along with new signs that read "Express Lane" were required by new federal regulations to adequately warn drivers they were entering special lanes reserved for carpools, motorcycles, buses and solo drivers that pay to use them.

That seemed counterintuitive to Drive reader Chris, who wondered why MnDOT dug into the new pavement to place the EXPRS signage on the roadway. "Why wouldn't they simply paint that signage on the road similar to the lane striping? Won't this cause the roadway to deteriorate faster in these sections where they abraded the new surface?" he asked in an e-mail.

Goodness knows our roads take a beating and don't need any extra gouges, but in this case the indentations won't cause any harm, said Tim Clyne, a materials engineer with MnDOT's Metro District.

"The shallow depth that our pavement markings are ground in does not noticeably shorten the pavement life," he said.

A MnDOT traffic engineer said by grooving the markings into the pavement, they last longer and are protected from plowing operations. The top of the pavement marking sits at or just below the top of the road surface (as opposed to on the surface like painted lines do), and that allows plow blades to pass over the top of them. Thus they don't get scrapped off as easily as lines do.

Motorists may "feel" the pavement markings as they drive over them, the engineer noted. Typically, a marking is grooved into an area slightly bigger than needed. Because the area is often wider than the distance between a vehicle's tires, drivers will "feel" the marking when hitting the groove.

MnDOT spokesman David Aeikens says the agency will bring out the wrecking ball and start tearing down the deteriorating Nine Mile Creek bridge on Jan. 10, marking the start of a $64 million project that will keep the segment of Hwy. 169 between Bren Road in Minnetonka and 5th Street/Lincoln Drive in Edina closed for most of 2017.

During the bridge's closure, motorists will be funneled onto Hwy. 100, I-394, I-494 and the Crosstown. Take note, the ramp from westbound I-394 to southbound Hwy. 169 will also close Jan. 10.

The new raised bridge that will look something like a causeway over the low marshy area is just the start. Come April, Hwy. 169 drivers will face more headaches when 6 miles of pavement are rehabilitated between the Crosstown and Hwy. 55. That will bring traffic down to a single lane in each direction. By summer the exit and entrance ramps at 16th Street in St. Louis Park will close permanently. Better acceleration and deceleration lanes will be built at Cedar Lake Road. You've been warned.