4 Roadway Conditions
4.1.5 Target Crash Population
The automated ice detection and warning system in Wyoming targets the population of crashes that occur on bridges during icy conditions.
According to a FARS query,(2) approximately five fatal crashes occurred on rural bridges during icy conditions in 1998. Crashes occurring on bridges were identified by examining the first harmful event. Any crash with a first harmful event of hitting a bridge parapet end, a bridge pier or abutment, or a bridge rail were considered to have occurred on a bridge.
This system is another system that should address a larger population of non-fatal crashes. This type of system should hold maximum potential payoff for remote bridge locations subject to freezing and experiencing frequent sliding crashes.
It should be noted that the number of crashes from ice on bridges may be underestimated because these crashes may get coded as “too fast for conditions.” Drivers may start skidding and losing control because of the ice on the bridge, but do not crash until they are off the bridge.
Two of the anti-icing systems, the North Dakota and Wisconsin de-icing systems, also target the same small population of fatal crashes discussed above. Again, these systems are aimed more at non-fatal sliding crashes. These two systems, however, take an active approach to dealing with the icy bridge deck. Thus, instead of providing a warning that the hazardous condition exists, the system senses and removes the hazardous condition. These systems should provide maximum potential payoff when deployed on bridge decks that are subject to freezing and have a history of frequent crashes under icy conditions.
The New York anti-icing system targets icy and snowy curves instead of icy bridges. According to a FARS query (2) in 1998, 233 fatal rural crashes occurred on curves with a pavement surface condition of ice, snow, or slush. Such systems should provide maximum potential payoff for remote shaded curves, subject to ice or snow buildup, and with a history of frequent crashes during these conditions.