4 Roadway Conditions
4.2.5 ITEM Hazelight Fog©
Impetus for the Activity
The Hazelight Fog© system was developed because of the diminished performance of conventional road studs [raised pavement markers or RPMs] in foggy conditions. Conventional studs depend on vehicle headlights to provide enough light to reflect back to the driver, whereas Hazelight Fog© is not dependent on vehicle headlights to be visible to the driver.(8 )
Description of the System
The system is installed in a number of locations in the UK and Canada, and has been proposed for use in Mexico, Japan, and West Virginia. The objective of the system is to combat fog-related crashes by providing improved delineation for drivers during low visibility events (fog, rain, mist).
The system consists of several in-roadway signal units placed on the centerline and/or edge line. Each unit can sense fog, rain, and mist, using built-in environmental sensors, and trigger its LEDs (output) if these low visibility conditions exist. The units are solar-powered, and are charged by daylight and by vehicle headlights.
An optional feature with this system is the ability to forewarn drivers of a vehicle in front of them. The units detect the presence of vehicles, and leave a trail of flashing amber LEDs (trail function) to warn vehicles following behind. If the following vehicle is detected within 4 seconds of the leading vehicle, the amber warning changes to red (tailgate function).
Both flush-mounted units, and units resembling conventional RPMs are available. Units can also be mounted on posts and barriers, if desired.
It is expected that deploying this system will reduce or eliminate multivehicle crashes during low visibility conditions wherever it is installed.(9 )
System Performance
The French National Laboratories at Cleremont Ferrand have verified the system’s fog detection and LED perception. The advertised operational life is up to 6 years. It is also advertised that the units will display their warnings for several weeks on a single full solar charge.