Work zone intrusion alarm effectiveness.

Krupa, Cathy · 2010 · ROSA P / New Jersey. Dept. of Transportation

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Summary

This report evaluates the effectiveness and worker acceptance of the SonoBlaster!® Work Zone Intrusion Alarm, a mechanical safety device designed to protect highway maintenance workers from errant vehicles. Commissioned by the New Jersey Department of Transportation (NJDOT) and conducted by Cambridge Systematics, Inc., the study aimed to determine if the device, which emits an audible alarm upon impact with a vehicle, could effectively warn workers and alert drivers in breach situations. The research was motivated by high national work zone fatality and injury rates and the Federal Highway Administration’s distribution of these units for trial deployment. The study design involved field observations and interviews with maintenance crews during routine lane closure operations. However, the scope was limited to a single pilot test conducted on U.S. Route 1 in South Brunswick, New Jersey, in May 2010. During this test, 14 SonoBlaster!®-equipped cones were deployed alongside standard cones to close a shoulder lane. No actual vehicle intrusions occurred during the observation period. To assess the device’s performance, researchers conducted two impact simulations: one involving a low-speed vehicle grazing the cones and another involving a manual push-over of a cone. The study was terminated early because NJDOT could not schedule additional lane closure operations, and preliminary findings raised significant concerns about the device’s reliability. The pilot test yielded mixed results regarding functionality and usability. The alarm’s sound volume and duration were deemed satisfactory, audible at distances of at least 200 feet even when workers wore ear protection. However, the study could not determine audibility during loud equipment operations, such as jackhammering, as those conditions were not simulated. Significant operational issues were identified: mounting the devices to cones was time-consuming, and the setup process was difficult. Most critically, the device exhibited poor quality control and reliability. Several units fired prematurely while in the locked, unarmed position during transport and preparation, and the visual indicator for verifying the cocked mechanism was inconsistent. Additionally, the mounting bracket broke when a cone was dropped from a height of three feet, indicating durability issues. The study concludes that the SonoBlaster!® alarm is not desirable for deployment on NJDOT maintenance jobs due to reliability problems, quality control issues, and cost. The frequent misfires and difficult setup procedures outweighed the benefits of the audible warning. Because no actual intrusions occurred, the study could not definitively answer whether the device effectively prevents injury or improves worker safety perception. NJDOT determined that further testing would not alter these conclusions, suggesting the device may be more practical for lower-speed municipal roads rather than high-volume highway maintenance.

Key finding

The alarm was audible at 200 feet during simulations, but the device suffered from premature firing in the locked position and fragile mounting brackets, leading NJDOT to deem it unreliable and impractical for deployment.

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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• emergency work zone conspicuity
• auditory warnings