Evaluation of Work Zone Split Traffic Symbol Sign: Final Report

Edara, Praveen K.; Sun, Carlos; Brown, Henry; Leight, Shawn; Nketah, Emmanuel · 2017 · ROSA P / Missouri. Department of Transportation

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Summary

This study evaluates the effectiveness of an alternative "split traffic symbol" sign for freeway work zones where a middle lane is closed, requiring traffic to shift to both sides. The research was motivated by concerns that standard Manual on Uniform Traffic Control Devices (MUTCD) signage, which uses two separate signs to indicate lane shifts, may cause confusion if drivers miss one sign, potentially leading to aggressive lane changes. The alternative sign consolidates the lane arrangement information into a single graphic. The evaluation was conducted at a bridge rehabilitation work zone on Interstate 170 in St. Louis, Missouri, during December 2016. The researchers employed a mixed-methods approach to assess driver behavior, safety, and operational impacts. Data collection included stationary and drive-through video recordings to analyze traffic counts, lane change rates, and sign visibility. Stakeholder interviews were conducted with Missouri Department of Transportation (MoDOT) personnel and contractors to gauge their perceptions of the signage. Additionally, the study analyzed crash data from 2015 and 2016 to identify safety trends and used Regional Intelligent Transportation Information System (RITIS) data to measure travel times during the work zone period compared to historical baselines. Findings from video analysis indicated that the alternative sign was sufficiently visible, with average detection distances of 1,637 feet northbound and 1,043 feet southbound. Lane change rates decreased between the early and late construction periods, suggesting drivers adapted to the signage and work zone layout over time. Most lane changes occurred between the outside and middle lanes, consistent with the gore point location. Stakeholders generally viewed the alternative sign favorably, noting it communicated lane arrangements more clearly than MUTCD signs, though opinions on safety improvements were mixed. Driver feedback via MoDOT’s online survey revealed no concerns regarding the new signs. Crash analysis showed that patterns during the work zone period were similar to pre-work zone conditions, and the alternative sign was not a contributing factor in any crashes. Operational analysis found no significant differences in travel times attributable to the signage. The study concludes that the alternative split traffic symbol sign effectively communicates lane closure information without causing adverse impacts on safety or traffic operations. The consolidation of lane information into a single sign appears to reduce driver confusion and facilitates smoother traffic flow through complex work zones. The results support the potential for broader adoption of such alternative signage in freeway work zones involving middle lane closures.

Key finding

The alternative split traffic symbol sign communicated information clearly to drivers without causing adverse impacts on work zone safety or travel times, and drivers adapted to the signage as lane change rates decreased during later construction phases.

Methodology

mixed_methods

Sample size: 32350

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

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
• perceptual countermeasures