Commuters driving through construction on Interstate 94 east of downtown St. Paul have noticed something weird.

The freeway is expanding and contracting every day, like the lungs of some huge animal.

In the morning — inhale — the highway expands to more westbound lanes. In the evening — exhale — that section of roadway narrows.

The highway alchemy is accomplished by a relatively new machine — the Road Zipper, made by Nebraska-based Lindsay Corp. The bus-sized contraption can shift 10 miles of concrete barriers in one hour.

The machine is a new take on an old idea — reversible lanes. Engineers have long considered the idea of flexible roadways, for which the traffic direction can be changed according to demand.

For example, MnPASS lanes on Interstate 394 west of downtown Minneapolis alternate between east- and westbound depending on time of day. The change in traffic direction is made simply by opening and closing entries to the lanes.

Related Articles St. Paul man poured poisonous chemicals on ex-wife in Roseville park, according to attempted murder charges

Man, 38, dies of apparent natural causes at Ramsey County jail

Roseville: Man arrested after ex-wife suffers potential exposure to toxic chemical

Sept. 30 is last day for public comment on Pigs Eye Lake makeover

St. Paul woman sentenced for manslaughter in man’s death; murder charge dismissed But the idea of moving median barriers is relatively new. The Road Zipper has been used only twice before by the Minnesota Department of Transportation, according to Tiffany Dagon, traffic work-zone engineer for the department.

She said that during a project on Interstate 494 in Bloomington, the barriers were placed to accommodate traffic during the day. At night, the machine moved the barriers to narrow the flow of traffic and give construction crews more room.

On another I-494 project, in Plymouth, the Road Zipper was used as it is being used now — to expand and contract the number of lanes for the time of day.

Travelers are seeing the Road Zipper at work on the I-94 construction zone between Interstate 694 and Mounds Boulevard, where the road is being resurfaced

There is nothing more frustrating than being stuck in eastbound traffic and seeing all that westbound traffic flowing.”

The machine lifts the 1,500-pound barrier blocks, each about 3 feet long, and moves them, via a conveyor system, one lane over, putting them neatly in a row. The daytime switch is made around noon.

By fitting the roadways to traffic — instead of the reverse — the Road Zipper increases traffic flow and reduces road rage, said MnDOT spokesman Kevin Guttnecht.

“There is nothing more frustrating than being stuck in eastbound traffic and seeing all that westbound traffic flowing,” he said.

MnDOT engineer Dagon said the Road Zipper is used most commonly in construction zones. But some cities use it every day just to create extra lanes where they are most needed.

Could it be used every day to speed up traffic on busy highways such as Interstates 35E and 694?

Dagon won’t go that far, but did say MnDOT would continue using the Road Zipper in construction projects. “When you give people an extra lane,” she said, “there is a big benefit to that.”