Evaluation of the Smart Work Zone Speed Notification System

Hourdos, John; Parikh, Gordon; Dirks, Peter; Lehrke, Derek; Lukashin, Pavel · 2019 · ROSA P / Minnesota Traffic Observatory Laboratory

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Summary

This study evaluates the Smart Work Zone Speed Notification (SWZSN) system, designed to improve safety and reduce congestion in highway work zones. The system utilizes Portable Changeable Message Signs (PCMS) to inform drivers of downstream traffic speeds up to one mile ahead. The underlying hypothesis is that providing this information allows drivers to slow down earlier or perform smoother decelerations, thereby reducing the frequency of sharp braking and rear-end crashes. The research was motivated by the need to mitigate safety risks associated with lane closures and unpredictable queuing in urban freeway work zones, specifically during the reconstruction of a 4.4-mile segment of I-94 in St. Paul, Minnesota. The evaluation was conducted by the Minnesota Traffic Observatory between 2016 and 2017. Data collection involved video surveillance from nine camera stations, detector data from Wavetronix radar sensors, and PCMS message logs. Due to the high cost of comprehensive radar instrumentation, the researchers relied on computer-vision-based trajectory extraction from video footage to calculate vehicle deceleration rates. The study design compared driving behavior during periods when the SWZSN system was operational versus when it was offline. In 2017, camera positions were adjusted to optimize data extraction, and sensor calibration was improved to address issues identified in the first year, such as unreasonable or delayed messages caused by noisy speed data. The results indicated that the SWZSN system had a statistically significant influence on driver behavior, a finding noted as superior to many other driver alert systems. When the system provided consistent and accurate speed notifications, drivers exhibited beneficial reductions in deceleration rates, with decreases exceeding 30% in selected instances. However, the study also found that counterproductive or misleading messages, often resulting from algorithmic discrepancies or poor sensor calibration, prompted relative increases in deceleration rates. The analysis highlighted that the system’s effectiveness was heavily dependent on the accuracy of the downstream speed information provided to drivers. The significance of this research lies in its demonstration that downstream speed notification is an effective traffic control tool for work zones, distinct from advisory speed limits. The study concludes that while the concept is promising, the specific speed estimation and message generation algorithms require refinement to minimize misleading outputs. Additionally, the authors recommend using temporary detection on portable trailers rather than permanent sensors to allow for more strategic placement and easier calibration during complex construction staging. These findings provide actionable insights for transportation agencies aiming to deploy intelligent transportation systems to enhance work zone safety.

Key finding

The system resulted in beneficial reductions of selected decelerations by more than 30 percent when messages were consistent and accurate, and it exerted a statistically significant influence on driving behavior.

Methodology

naturalistic

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
• perceptual countermeasures
• automated enforcement cameras

Information type

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• Applied Guidance: countermeasure evaluation