The Maryland Department of Transportation is using a Road Zipper to move a concrete traffic wall to change lanes during bridge reconstruction over Libery Reservoir on Md. 140.
The Maryland State Highway Administration has elected to utilize a technology never before used in the state to ensure traffic along Md. 140 near the border of Carroll and Baltimore counties remains smooth while the bridge over Liberty Reservoir is rehabilitated.
A barrier transfer machine, otherwise known as a zipper machine, will be used to shift concrete lane dividers during rush hour to ease congestion between Old Westminster Pike and Glen Falls Road. The movable barrier is being paired with a light system — similar to what is used on the Bay Bridge — to indicate shifting traffic patterns.
Project Manager Mark Allen said SHA is planning to move the barrier into place Saturday, April 18.
During morning rush hour during the week, the barrier will be in place to allow for two lanes of traffic heading south toward Interstate 795. When early morning traffic dies down around 9 a.m., the barrier will be shifted, along with the accompanying light system, to indicate and allow for two lanes of traffic heading toward Westminster.
While the barrier is being shifted — a process Allen said takes about half an hour — there will be one lane of traffic in each direction.
During the weekend, the crew will maintain the same pattern as in the afternoons with two lanes of northbound traffic to accommodate commuters heading toward Westminster, he said.
The machine has a snake-like channel connected to the underside of the vehicle, which grasps the interlocking barriers — some weighing more than half a ton — and as the vehicle moves, shifts the barrier to the other side of the vehicle. The purpose of the machine is to accommodate increased traffic that varies depending on the time of day, Allen said.
"[The zipper machine] is actually pretty simple," Allen said. "We thought it would be more complex than it turned out to be."
The barriers are connected by steel pins, hence the reference to a zipper, said SHA employee Calvin Scheetz.
"It's kind of like a zipper on a jacket," Scheetz said. "It guides [the barrier] to where it needs to be and keeps it in one piece."
Other than easing congestion, the biggest advantage to using this system is how quickly and easily the barrier can be shifted, Allen said. Without the use of the zipper machine, it would take about three hours to place a stationary barrier along the roughly 2,000 feet of road between Old Westminster Pike and Glen Falls Road, he said. It will now take his crew just 30 minutes to do the same distance, Allen said.
"Another good thing, the machine is designed so that if it breaks down, it can be towed with a truck," he said.
The rehabilitation of the bridge began in winter 2013, and is part of the state's bridge system preservation program. It was constructed in 1946, and though it is structurally safe, bridge surveys have revealed signs of deterioration, said SHA spokeswoman Heather Keels.
The project will include the replacement of the bridge deck and supporting steel beams, as well as widening of the bridge shoulders, Keels said.
The current phase, which includes the replacement of the deck, is expected to be completed by winter, Allen said.
"We are looking at finishing [the current phase] in about 150 days," Allen said. "Anchor [Construction], the company contracted to do the work, has incentives if they complete the work on time."
The barrier will remain in place during this time, and due to the reversible traffic pattern, Old Westminster Pike will be closed to through-traffic, but local traffic will have access to Md. 140, Keels said.
"There's too much going on [to leave it open]," she said. "We know it's inconvenient, and we appreciate your patience. It will be very beneficial."
While the barrier is in place, speed limits will be reduced to 45 miles per hour and, for at least the first week, Maryland State Police troopers will increase activity in the area, Allen said.
"It's not the people that live here we are worried about," he said. "It's the people that don't know the work is going on."
The final phase of the project, which entails connecting the widened shoulder to the replaced bridge deck, is expected to be completed in the spring 2016. The total cost of the rehabilitation project is expected to be about $7.4 million.