DESIGN CONSIDERATIONS FOR TWO-LANE, TWO-WAY WORK ZONE OPERATIONS

A practice used during long-term construction activities on divided highways is to allow two-lane, two-way traffic operations (TLTWO) on one roadway while the other roadway is completely closed to traffic. Federal, state, and local officials have become increasingly concerned in recent years about safety problems in TLTWO work zones. This report presents the results of operational and accident studies of 36 construction sites employing either two-lane, two-way operations or lane closure traffic control. Project cost information for four TLTWO and ten lane closure sites was also analyzed. Results of the study were divided into four areas: evaluation of centerline treatments on the two-way roadway segment; design of temporary median crossover roadways; comparison of TLTWO and lane closure operations; and general results. The study of centerline treatments revealed that zones with double yellow centerline only had higher accident rates and the vehicle encroachment rate into opposing lanes is much higher than for any other type of centerline treatments studied. Accident rates with other centerline treatments do not support a requirement for portable concrete barriers in all TLTWO zones. Results of the study of median crossover design revealed lower accident rates and smoother speed transitions for crossovers with a flat diagonal design compared to those with reverse curve design. Comparisons of TLTWO and lane closure sites revealed that the lane closure alternative will be more cost effective than TLTWO traffic control unless substantial construction cost reductions could be realized with TLTWO. (FHWA)