Moveble barriers improve workzone safety, reduce costs

Two phases of an arterial reconstruction project in Salt Lake City have provided a compelling cost-based argument for moveable barriers.
January 25, 2012
Road Construction
Two phases of an arterial reconstruction project in Salt Lake City have provided a compelling cost-based argument for moveable barriers.

Construction has recently been completed on 3500 South in Salt Lake City, Utah, which was completely reconstructed by UDOT Region 2 from the Bangerter Highway to 2700 West to build Utah's first Bus Rapid Transit lanes. With a significant ADT that runs between 38,000 and 48,000 vehicles throughout the corridor, keeping traffic moving was the most important and the most difficult task during construction.

The first phase of the project called for two lanes to be open for traffic in each direction, and plastic barrels were used to separate directional traffic and to delineate the work zone. The work zone area was confined and restricted, and it lacked positive protection which created dangerous conditions as confused motorists occasionally turned into the work zone. In addition, accidents occurred when drivers made left turns into businesses through the barrels, which contributed to congestion. The contractor needed a larger, more protected work space, and the traffic management plan needed a way to limit the number of left-hand turn options for motorists without restricting traffic flow.

Phase II

For the second phase of the project, after reviewing several options, UDOT elected to employ a reversible lane using moveable barrier technology from 21 Barrier Systems International. The moveable barrier could keep two lanes open to traffic in the peak direction by using a total of only three lanes, instead of the four lanes required when using barrels. This would give the contractor an extra lane to expand the work zone, keeping workers safe and accelerating construction without causing additional traffic congestion.

• Use of moveable barrier on arterial reconstruction, Salt Lake City


• US$2.4 million in quantified benefits (4:1 B/C ratio)
• B/C ratio of greater than 10:1 with all benefits considered
• US$1million in accident savings
• Project accelerated by seven months
• User delay savings from early completion
• Savings from reduced accidents
• Lower impact to businesses on the corridor
• Contractor TRO saving
The barrier would also limit left-hand turns to five major intersections. 2.7 km of moveable barrier was deployed as a positive barrier separation between east and westbound traffic, and the barrier was moved multiple times daily to create a 1/2, 2/1 traffic pattern based on peak traffic needs. The barrier was transferred 3.7m, or one lane width, in one pass at 8km/h (5mph). The entire transfer took approximately 20 minutes, including repositioning the traffic control and signage.

With the expanded work zone, the contractor was able to use larger, more efficient equipment and work unimpeded for longer periods of time while the barrier was in place. This resulted in the elimination of one complete phase of construction, reducing the total number of phases from three to two. The accelerated construction schedule helped the contractor to finish the project seven months early. In a report commissioned by UDOT and compiled by T.Y. Lin International, the user delay savings from the early completion were estimated at US$1.3 to $1.4 million (vehicle operating costs were not included). The businesses on the corridor also benefited from the early project completion, which ended the disruption to business from the construction work zone. While the UDOT report did not quantify these benefits, it did consider them to be "significant"

Positive protection

The barrier limited left-hand turns except at five major intersections, which reduced accidents and helped keep traffic running smoothly. The report estimates that, based on the average number of left-hand turns in the corridor, the
barrier eliminated 20 to 25 left-turn crashes while in operation, with an estimated reduction in crash costs of an additional $1 million Safety was also enhanced for construction workers and motorists with the moveable concrete barrier. The positive protection provided by the barrier eliminated work zone encroachments.

The benefits that were determined from the use of moveable barrier included reduced user costs, shorter travel distances, improved safety, lower impacts to businesses, early project completion, less fuel use and reduced air emissions. The report conservatively estimated the total benefits of using moveable barrier on the project at between US$1.7 to $2.4 million, with a benefit/cost of 4:1 (considering user delay costs and accident savings only). The authors also stated that if all benefits were considered (such as the reduced air emissions and benefits of early completion for businesses), the benefit/cost ratio for the moveable barrier system would be greater than 10:1.
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