Evaluation of the Performance of Portable Precast Concrete Traffic Barriers

About the report:

The portable precast concrete traffic barrier is used to separate high speed vehicular traffic and construction activities. However, since there was a lack of information on the barrier's performance in a construction zone environment, officials of the Virginia Department of Highways and Transportation requested that the Virginia Highway and Transportation Research Council evaluate the performance of the barrier during the widening of the Virginia Beach-Norfolk Expressway (Rte. 44). The scope of the evaluation included (1) a review of the literature on the performance of the concrete "safety shape" barriers, (2) an examination of the accident data before and during construction on Rte. 44 to determine the effects of construction on the frequency and characteristics of traffic accidents, (3) an analysis of tire marks and barrier-involved accidents to determine the effectiveness of the barriers in safely redirecting vehicles, and (4) an examination of the effects of construction on traffic characteristics. The literature review revealed that in using the precast concrete traffic barrier the following factors should be considered: (1) the end of the barrier should never be exposed to oncoming traffic; (2) the barrier joints must be tight for the barriers to act as a system; (3) the longitudinal axis of the barriers should be placed parallel to the roadway, except when the barrier system is started with a flare; (4) the barrier system should have a minimum length of 100 feet (30 m); and (5) the barrier system must have lateral support in order to prevent vehicle penetration. For conditions on Rte. 44, it was found that (1) there was an average of 49 vehicle contacts with the barrier for every reported accident in which the barrier was involved; (2) there was a definite tendency for motorists to stay out of the barrier lane, but avoidance of the barrier lane was reduced as volume increased; and (3) with a 55 mph (88 km/h) posted speed limit, the vehicular speeds were reduced by only a few miles per hour when the barriers were in place. Evaluation of the barrier's performance during the widening of I-95 is recommended, since that highway carries a much higher volume of tractor-trailers than does Rte. 44.

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