Intelligent Transportation Systems in Work Zones: A Case Study: Dynamic Lane Merge System: Reducing Aggressive Driving and Optimizing Throughput at Work Zone Merges in Michigan

NHTSA · 2004 · ROSA P / United States. Federal Highway Administration

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Summary

This case study examines the deployment of a Dynamic Lane Merge (DLM) Intelligent Transportation System (ITS) during a major reconstruction project on Interstate 94 (I-94) in Clinton Township, Michigan. The research addresses the safety and mobility challenges associated with work zone lane closures, specifically the "late lane merge" phenomenon where drivers delay merging, leading to aggressive driving, speed variability, and increased crash risk. The Michigan Department of Transportation (MDOT) implemented the system to smooth traffic flow, reduce aggressive maneuvers, and optimize throughput at a three-to-two lane transition. The DLM system, developed by International Road Dynamics Inc., consisted of five trailers spaced 1,500 feet apart upstream of the work zone. Each trailer was equipped with microwave radar sensors to detect traffic volume, speed, and occupancy, as well as flashing "Do Not Pass" signs. The system calculated an "Activity Index" based on sensor data; when this index exceeded preset thresholds, it automatically activated upstream signs to enforce early merging. The system operated on a closed-loop wireless communication network and was leased for approximately $120,000. Deployment occurred during the 2002 and 2003 construction seasons on westbound I-94, with active police presence provided by the Michigan State Police to support enforcement. Evaluation results indicated that the system met its primary objectives. During the morning peak period, average travel time delay decreased from 95 seconds to 69 seconds per vehicle per 10,000 feet, and average travel speed increased from 40 mph to 46 mph. The average number of stops per probe vehicle run dropped from 1.75 to 0.96. Safety metrics improved significantly: aggressive driving maneuvers during the afternoon peak period fell from 2.88 to 0.55 per run, and crash data showed zero reported crashes in the two months following implementation, compared to an average of 1.2 crashes per month prior to the system's activation. A cost-benefit analysis by Wayne State University determined the system was cost-effective if the value of user time exceeded $3.33 per hour, a threshold well below standard transportation valuations. The study concludes that DLM systems are effective for managing traffic at work zones with peak hour volumes between 3,000 and 3,500 vehicles per hour for three-to-two merges. Key lessons learned include the importance of early stakeholder engagement, particularly with law enforcement, and the need for adequate site width for trailer placement. The system requires line-of-sight communication and stable work zone geometry to avoid frequent recalibration. Public awareness campaigns were essential for driver compliance. The findings suggest that dynamic ITS applications can significantly enhance safety and mobility in work zones when deployed under appropriate traffic conditions.

Key finding

The Dynamic Lane Merge system reduced aggressive driving maneuvers from 2.88 to 0.55 per travel time run during the afternoon peak and eliminated crashes in the merge transition area during the two-month evaluation period.

Methodology

field_study

Provenance

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

Topics

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• work zones
• emergency work zone conspicuity