Investigation of Alternative Work Zone Merging Sign Configurations [2013]

Edara, Praveen; Zhu, Zhongyuan; Sun, Carlos · 2013 · ROSA P / Mid-America Transportation Center

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Summary

This study investigates the effectiveness of an alternative merge sign configuration in freeway work zones to improve safety and driver behavior. The research was motivated by findings that the advance warning area immediately preceding a lane closure taper exhibits the highest crash rates in work zones. The Missouri Department of Transportation (MoDOT) sought to evaluate a new temporary traffic control plan that replaces the standard Manual on Uniform Traffic Control Devices (MUTCD) graphical lane closed sign with a text-based "MERGE/arrow" sign on the closed-lane side and a "RIGHT LANE CLOSED" sign on the open-lane side. The primary goal was to determine if this alternative signage encourages earlier merging, thereby reducing conflicts near the taper. The experimental design involved field studies at a short-term work zone on westbound Interstate 70 near Boonville, Missouri, involving a left lane closure. 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 test sign. Researchers used video monitoring to track vehicle positions and radar guns to record speeds at the merge sign (1,000 feet upstream of the taper) and at the taper (400 feet upstream). The study analyzed open lane occupancy—the proportion of traffic in the open lane—at various distances from the merge sign and compared speed statistics, including mean, standard deviation, and 85th percentile speeds, using statistical tests such as t-tests, F-tests, and Cohen’s effect size measures. The results indicated that the test sign significantly improved open lane occupancy upstream of the merge sign. Specifically, the test sign encouraged up to 11% more traffic to occupy the open lane at locations upstream of the merge sign compared to the MUTCD sign. This difference was most pronounced for passenger cars, which stayed in the closed lane longer than trucks under both conditions. Truck drivers exhibited safer merging behavior regardless of the sign type, with over 90% merging upstream of the sign in both scenarios. Downstream of the merge sign, occupancy rates for both configurations were similar. Speed analysis revealed no substantial differences between the two signs; while 85th percentile speeds were statistically lower by 1–2 mph with the MUTCD sign, the practical magnitude of these differences was negligible. The study concludes that the alternative text-based merge sign is a viable and effective alternative to the standard MUTCD graphical sign. By encouraging vehicles, particularly passenger cars, to merge earlier, the test sign promotes safer driving behavior by reducing the likelihood of conflicts near the taper. The findings suggest that MoDOT and other agencies may consider adopting this signage configuration to enhance work zone safety without negatively impacting traffic speed or flow.

Key finding

The alternative merge sign configuration increased open lane occupancy upstream of the merge sign by up to 11% compared to the standard MUTCD sign, while speed characteristics remained statistically similar between the two configurations.

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