"I was looking at a low-boy trailer, wishing the guy would get out of the way, when I thought, what if we tipped the low boy on its side?" Groeneweg recalls. "That was the idea for the MBT-1."

The basic MBT-1, generally painted yellow for good visibility, includes a standard tractor-trailer pulling wall sections measuring 20 ft long and 5 ft high. As many as three wall sections can be used, making the entire barrier 42 to 102 ft long. Adding a truck-mounted attenuator (TMA) to the rear adds another 17 ft. An MBT-1 can cost $300,000, which, amortized over a 20-year lifespan, is around $15,000 a year, according to the Mobile Barriers website.

To demonstrate the product's effectiveness, Walt Black, Mobile Barrier's vice president of equipment, told the story of four highway construction crewmen on a job in San Antonio, Texas. They were eating lunch behind a movable barrier when a distracted driver hit the barrier going 75 miles an hour. "Those guys said they would have been dead if not for the barrier," Black says.

California-based Barrier Systems, a subsidiary of Omaha-based transportation, industrial and agricultural solutions conglomerate Lindsay Corp., introduced its QuickChange Movable Barrier in the mid-1980s. Now called the Road Zipper System, the technology pins together one-meter sections of reinforced concrete to form a barrier wall, which is controlled by a barrier transfer machine (BTM) that lifts the barrier and passes it through a conveyor.

Though movable barriers are used mostly for roadwork so far, some barrier makers are marketing them for other projects. They can become portable security measures for oil wells, hospitals, government buildings and the like, where they can become rolling perimeters that augment a front gate or enhance checkpoints and inspection stations. Barrier Systems also envisions using them to create disaster evacuation routes in areas like the East and Gulf coasts during hurricane season.

While Barrier Systems uses the Road Zipper largely on highway construction and traffic-management projects, it also has made bridges a specialty, working on the Golden Gate Bridge in San Francisco as well as spans in cities from Philadelphia to Auckland, New Zealand.

"Our movable barrier is used for long projects—long in calendar length and long in linear terms. Cones are cheap and fast, and if you care about safety, you put up a concrete barrier," says Chris Sanders, senior vice president of Lindsay Transportation Solutions, who some industry experts call the "godfather" of movable construction barriers. "If you care about all those things, you do a movable barrier."

Movable barriers also improve traffic flow on road construction projects because they can be used to add or decrease lanes faster than cones or barricades can, experts note. "Our product is very expensive compared to cones and portable barriers, whether they're steel or concrete—two to four times more expensive," says Sanders. "But it's really about mobility, moving lanes back and forth."

Researchers are now studying the effectiveness of movable barriers. Oregon Dept. of Transportation and Oregon State University released a report in 2013 that looked at Mobile Barriers' MBT-1. The study found that because of the barrier, construction workers felt more protected and were able to perform better, and traffic benefitted from being able to move faster than with other safety devices. The study called the barrier "an effective and beneficial tool."