This week's column on scars that are left behind when temporary lane markings are removed from metro area highways spawned a number of comments from readers who said they have been confused or witnessed others who have.
Most of the commenters complained about the remnants of temporary markings on 494 in the vicinity of Cedar Avenue where there has been lots of construction in the past year. Others said the area around 494 and 169 in Eden Prairie was a problem area, and other singled out the grooves on Hwy. 100 between 36th Avenue and 42nd Avenue in Robbinsdale.
One driver, who called them "ghost lines," said "with rain, early morning darkness, and the glare from the lighting, it is almost impossible to determine the correct lane markings. Surprised there aren't more serious accidents caused by this problem."
Another driver who noticed the obsolete lines on 494 at Cedar and "almost made the lane change, too" suggested that MnDOT sandblast away the unneeded lines and then paint over them with a color close to the pavement.
Others wanted to know why MnDOT doesn't use tape when putting down temporary lines. For one, it is very expensive. Second, it must be applied in warmer conditions that allow the adhesive to stick to the road, and finally unless it's grooved into the pavement, snowplows will peel it right off.
MnDOT does use tape to put down permanent lines when they need to last five to seven years. But it is used primarily when the pavement still has a long lifespan. 
The agency uses epoxy to mark pavement when its life expectancy is between two and five years, and latex when lines will last a year or less. Latex lasts the least amount of time, and it is the least expensive substance to paint the roads, said Tiffany Dagon, a metro pavement engineer for MnDOT.
Others asked why MnDOT doesn't use reflective paint. The glass beads that reflect light to drivers work well when the pavement is dry, Dagon said, but when it's wet they don't reflect very well and don't send enough light back to drivers.
Snowplows also will scrape away those beads, "so they don't last very long."  New products that could combat this problem are coming on the market, and MnDOT is looking at them. However, "they are expensive," Dagon said.
A few readers had questions about roads where lane markings are absent or change abruptly.
One reader was unsure about the lane configuration on the Plymouth Avenue Bridge in Minneapolis and the roads leading up to it.
The bridge itself is stripped for two lanes in each direction, but on the east side of the bridge where it's called 8th Avenue NE., the road is wide enough for two lanes. However it's really just one, said Casper Hill, a city of Minneapolis spokesman.
The road was repaved as part of rehab work on the Plymouth Avenue Bridge and the segment between Sibley Street and Marshall Street  includes room for parking.
But without any lane markings to that indicate that the extra room on the side is really a parking bay, it's not intuitively obvious to motorists that the road snakes down to a single lane once they are off the bridge and approach Marshall.
Compounding the issue in the area is that on 8th Avenue east of Marshall there is a double set of yellow lines that serve as the center line. A new set of lines was recently put down to accommodate a left turn lane for westbound drivers, but the previous centerline marking, albeit faded, still shows through. That makes it harder for drivers to know which lane markings to follow.
"In the spring we will get out there and work harder to remove the old faded center line," Hill said. "And we'll repaint the new one."
 Photo credit: MnDOT

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Keeping an eye on Thursday's morning commute

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8:45 a.m. update: Problem free for the most part