Innovations - Movable Barriers in Work Zones
PDF Version (67 kb)
Hinged sections make repositioning barriers easier
Movable barrier technology allows for quick barrier adjustments to create protected work spaces or to reallocate travel lanes in the work zone to match time–of–day traffic flow fluctuations. Unlike traditional barriers, which are difficult and time consuming to reposition, movable barrier sections are interconnected and designed to be picked up and moved as a unit using a conveyer system.
Traditional concrete traffic barriers are used in many work zones to provide separation between work areas and moving traffic as well as between opposing directions of travel. They serve two purposes:
- To create or expand protected work spaces for highway crews during offpeak traffic periods by positioning the barrier outside of the travel lane during the peak-period, then moving it into the traffic lane for the period of work activity. The barrier is then moved back off of the roadway before the start of the next peak period to allow traffic to use more or all of the travel lanes.
- To create a median separating two opposing traffic flows where peak-period travel is higher in one direction in the morning and in the opposite direction in the afternoon. In this situation, the movable barrier positioned in the middle of the roadway can be moved to borrow a lane from the offpeak direction and allocate it to the peak direction of traffic flow. When the next peak period arrives, the process is reversed. This allows the space allocated to traffic to be used more efficiently, and allows a larger work space to be created for highway crews.
Movable barriers are constructed from a series of interconnected sections of barrier hinged together with steel pins to create a movable "chain." The T-shaped top of the barrier is specially designed to allow it to be picked up and moved laterally on a conveyer system by a self-propelled barrier transfer machine (BTM). As the BTM moves along the roadway, rubber wheels run along the underside of the T-shaped top, lift the barrier several inches off of the ground, and move it through an elongated "S" shape until it is repositioned laterally in its desired location. The amount of lateral shift of the barrier can range from 4 to 18 feet. The BTM can move at speeds up to 5 miles per hour (mi/h), allowing protected work spaces to be created in a matter of minutes.
The following projects show the improved efficiencies highway agencies and contractors can realize when they employ movable barriers:
- In 2005, moveable barriers were used to reallocate travel lanes for peak-period travel during a bridge reconstruction project on Interstate 94 in Wisconsin. This allowed the contractor to work on one span of the bridge at a time while the other span carried the traffic. Use of the barrier allowed travel speeds to remain acceptable during peak periods (51 mi/h). The project was completed in one construction season instead of two.
- Movable barriers were used during the widening of I–66 in Virginia just outside of Washington, DC. The barrier was positioned in the median and moved out to close the median travel lane during 4–hour midday work periods and longer work periods at night. Construction was completed 30 percent faster than expected, about 5 months ahead of schedule. Public interest in the commuter–friendly equipment used during the project resulted in a request to have it displayed at the local county fair.
For More Information
- "Movable Barriers for High–Traffic Work," Public Works, February 2000
- "Improving Highway Safety," Construction Today, December 2006, pp. 200–201
- Movable barriers Web site, www.barriersystemsinc.com
Team Leader, Work Zone Mobility and Safety
Office of Operation