4 Roadway Conditions
4.2.6 Target Crash Populations
Fog
The North Carolina fog detection and early warning system and the Trail-Light Systems target the same population of crashes as the VSL Fog category, and should achieve maximum potential payoff in similar situations.
Visibility – Snow and Dust
The Idaho Storm Warning System and the I-69 Visibility Detection System in Indiana target the population of crashes involving reduced visibility due to blowing snow or dust. It can be determined from Table 2, that approximately 2 percent or 472 of the 1998 rural fatal crashes (for which atmospheric condition and road class were known) happened under conditions of snow or smog, smoke, blowing sand, or dust. While this is a relatively small population of crashes, these systems should hold the maximum potential payoff when applied to localized areas with frequent, unpredictable, and severe visibility problems.