Safety Effects of Two-Lane Two-Way Segment Length Through Work Zones on Normally Four-Lane Divided Highways

In 1979, an equation was derived for the optimum length of two-lane two- way (TLTW) segments through work zones on normally four-lane divided highways. Solution of this equation for the prevailing conditions on I- 80 in Nebraska in 1986 yielded optimum segment lengths that were about 60 percent longer than those used previously in Nebraska. Because of concern expressed about the safety of longer TLTW segments, the applicability of the longer optimum lengths was questioned. The objective of this study was to determine the effects of longer TLTW segments on the safety of traffic operations. The study examined the relationships between segment length and five speed distribution parameters used as indicators of traffic safety. The relationship between segment length and TLTW accident rate was also examined. No relationships were found between TLTW segment length and accident rate or any of the speed distribution parameters. It was concluded that there is no relationship between TLTW segment length and the safety of TLTW operations for the conditions studied.