Idaho Storm Warning System Operational Test

Kyte, Michael; Shannon, Patrick; Kitchener, Fred · 2000 · ROSA P / United States. Federal Highway Administration

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Summary

The Idaho Storm Warning System Operational Test evaluated the feasibility of using advanced weather and visibility sensors to provide early warnings to motorists and transportation officials regarding dangerous driving conditions. Initiated in 1993 by the Idaho Transportation Department (ITD) and the U.S. Department of Transportation, the project was motivated by 18 major traffic crashes between 1988 and 1993 on a rural section of Interstate 84 in southeastern Idaho. These incidents involved 91 vehicles, resulting in nine fatalities and 46 injuries, with poor visibility identified as a primary contributing factor. The study aimed to determine if sensor data displayed on Variable Message Signs (VMS) could reduce vehicle speeds to safe levels during low-visibility events caused by snow, fog, or dust. The research was conducted in two phases over seven years. Phase I focused on evaluating the accuracy, reliability, and cost-effectiveness of three visibility sensor systems: Handar-Belfort, SSI-Belfort, and SSI-WIVIS. Sensors were installed near the Cotterell Port-of-Entry alongside automatic traffic counters that recorded vehicle speed, lane, and length. A video camera aimed at target signs at known distances served as a ground-truth verification method. Phase II assessed driver response to VMS information. Four VMS were installed along the corridor to display weather warnings. The evaluation compared vehicle speeds during adverse weather conditions with and without active VMS messages, analyzing data from low visibility, high winds, and heavy precipitation events. Phase I results indicated that the sensors provided reasonable visibility estimates. The three sensors agreed on visibility classifications (above or below 0.23 miles) 83% of the time, while the Handar-Belfort and SSI-Belfort sensors agreed 97% of the time. These two were deemed the most reliable, whereas the SSI-WIVIS sensor showed poorer correlation with the others and video confirmation. The system operated reliably after initial power and communication issues, with minimal maintenance costs. Phase II findings revealed that drivers naturally reduced speeds during poor weather even without VMS information. However, when VMS were operational during extreme conditions such as high winds and severe weather, drivers significantly reduced their speeds. This effect was most pronounced in the southbound direction, where drivers received advance warning from the signs. In isolated low-visibility events with otherwise ideal conditions, the VMS had no apparent effect on speed, though data availability for these specific scenarios was limited. The study concludes that providing real-time weather information to drivers encourages speed reduction during hazardous conditions, thereby enhancing safety. The project demonstrated the operational viability of integrating sensor data with VMS for traffic management. Following the test, ITD expanded its network, operating 24 road weather information stations and planning further installations. The findings support the use of such systems to maintain highway efficiency and safety during winter weather, validating the technology's role in Intelligent Transportation Systems.

Key finding

Drivers reduced their speeds more significantly during periods of high winds and extreme weather when variable message signs were operational compared to when such information was not provided.

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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• weather rain fog snow