LYNNWOOD — Detour ahead. We mean it. Never mind.

The state Department of Transportation has scrapped its original plan on a bridge at Ash Way and pulled the plug on its high-tech detour system on I-5, saying truck drivers just weren’t getting it.

"We’re all shocked this didn’t work. We had signs, flashing lights and extra enforcement from the Washington State Patrol. We sent out thousands of fliers. We thought it was a no-brainer," said Brian Dobbins, assistant project engineer.

The department announced Monday it will change how it will build the bridge and eliminate the detour for trucks. The change is expected to cost more money and take a couple more weeks to finish.

"We don’t know how much more it will cost. There’s a ballpark but I’m not comfortable giving that out until we talk to the contractor," Dobbins said.

The department had planned to build the bridge using a temporary scaffolding that required trucks 14 feet 6 inches and taller to detour around the construction.

Last month, it switched on three roadside lasers to measure the height of the trucks, warning drivers to take a detour at 128th Street SW.

But every day about 40 percent of the truckers ignored the restrictions, Dobbins said.

The drivers failed to drive in the far right lane so the lasers could measure the height of the truck, or they didn’t take the detour when they should have, he said.

The department delayed construction on that part of the bridge for a week. It added flashing lights to the detour signs and talked to companies whose trucks violated the restrictions.

It wasn’t enough.

The change in building plans will still keep the project within its $18.43 million budget and its December deadline, Dobbins said.

The west end of the bridge will be built on temporary supports and lowered into place with jacks, Dobbins said. A detour won’t be necessary because clearance will be 16 1/2feet during construction.

"The part I don’t understand is why they chose to disrupt things when there obviously was another choice," said Sandy Lashbrook, a dispatcher for Everett Fuel &Lumber Distributors, Inc.

The Arlington-based company had instructed all its truckers to take the detour, adding at least 30 minutes to their routes.

Typically bridges aren’t built under such height restrictions but engineers figured it was the best way for this bridge, Dobbins said.

The bridge, a project between Sound Transit and the department, will directly connect the park-and-ride to the carpool lanes on I-5. About 160 buses will be able to go up and over the freeway and get into the carpool lanes without having to cross several lanes of traffic.

But the ramp is close to the park-and-ride, and buses are heavy, so the bridge can’t be too steep. The most efficient way to build the bridge was to use the temporary scaffolding, Dobbins said.

"We like to build bridges in place," he said. "We’ve never build bridges on jacks. It’s a very delicate process to lower a bridge two feet."

Dobbins and other project engineers thought the new warning system would make the project feasible and safe.

The state had never used the lasers to track the height of trucks traveling through construction zones before now.

The first laser alerted drivers to take a detour. A second alerted drivers to pull over and wait for a trooper. A third served as a warning system for crews working on the bridge if an oversized truck was headed toward the bridge.

What the state learned, he said, is that it can’t trust truckers to simply take detours. "Now we can’t go back to the way we used to work," Dobbins said.

The department plans to keep the laser system, which cost between $200,000 to $250,000, working at the site. The warning signs will be turned off but the department will collect data about overheight trucks on the freeway.

That type of data doesn’t exist, Dobbins said. The information could be used to update state bridge design standards.

"I don’t think it was a huge mistake. We learned we can’t have low-height scaffoldings in this area. Maybe that information means we change design standards and no temporary bridges can be below 16 1/2feet," he said.

Reporter Diana Hefley: 425-339-3463 or hefley@heraldnet.com.