Investigation of Alternative Work Zone Merging Sign Configurations [2014]

Edara, Praveen; Sun, Carlos; Zhu, Zhongyuan · 2014 · ROSA P / Missouri. Department of Transportation

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Summary

This study investigates the effectiveness of an alternative merge sign configuration in freeway work zones, motivated by research indicating that the advance warning area immediately preceding a lane taper exhibits the highest crash rates. The Missouri Department of Transportation (MoDOT) sought to evaluate whether replacing the standard Manual on Uniform Traffic Control Devices (MUTCD) graphical lane closed sign with a text-based configuration—specifically a MERGE/arrow sign on the closed-lane side and a RIGHT LANE CLOSED sign on the open-lane side—would improve driver behavior and safety. The researchers conducted field studies at a short-term work zone involving a left lane closure on westbound Interstate 70 near Boonville, Missouri. Data were collected on two separate days under similar weather and traffic conditions, with one day featuring the standard MUTCD sign and the other the alternative "test" sign. The experimental design utilized three synchronized cameras to track vehicle trajectories and determine merge locations, along with radar guns positioned at the merge sign (1,000 feet upstream of the taper) and the taper start to record vehicle speeds. The study analyzed open lane occupancy, defined as the proportion of traffic in the open lane at specific distances from the taper, and compared speed statistics, including mean speeds, standard deviations, and 85th percentile speeds, using statistical tests such as the Z-test, t-test, and Cohen’s effect size. The results indicated that the alternative test sign significantly improved upstream merging behavior. Open lane occupancy was higher for the test sign compared to the MUTCD sign at locations upstream of the merge sign, with the test sign encouraging up to 11% more traffic to occupy the open lane early. This effect was most pronounced among passenger cars, which stayed in the closed lane longer than trucks under both configurations. Truck drivers exhibited safer merging practices regardless of the sign type, with over 90% merging upstream of the sign in both scenarios. Regarding speed, the analysis revealed no substantial practical differences between the two sign configurations. While the 85th percentile speeds were statistically slightly lower with the MUTCD sign (1 mph lower at the merge sign and 2 mph lower at the taper), the effect sizes were small, indicating negligible impact on speed compliance. The study concludes that the alternative text-based merge sign is a viable and potentially superior alternative to the standard MUTCD graphical sign. By encouraging vehicles to merge earlier and occupy the open lane further upstream from the taper, the test sign reduces the likelihood of merging conflicts near the lane drop, thereby enhancing work zone safety. The findings suggest that MoDOT and other transportation agencies may consider adopting this signage configuration to improve traffic flow and safety in stationary lane closure work zones.

Key finding

The alternative merge sign configuration increased open lane occupancy upstream of the merge sign by up to 11% for passenger cars compared to the standard MUTCD sign, while speed characteristics remained largely similar.

Methodology

field_study

Sample size: 2019

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• work zones
• emergency work zone conspicuity
• signage environment