Dense Fog
a Major Traffic Hazard in Wisconsin

Dense fog occurs during every month of the year in Wisconsin. It is more common during the cooler months of September through April. During the fall and spring months dense fog favors the early morning hours, while during the winter months dense fog can occur just about any time if certain weather conditions come together.

Sometimes the dense fog becomes widespread and lowers visibilities to less than 1/4 mile... or even down to near zero when they become a deadly traffic hazard.

The Wisconsin State Patrol rates dense fog as probably the most dangerous weather-related traffic hazard, with icy or snow-covered roads being in second place. The Wisconsin Department of Transportation/s statistics back up this believe with real numbers. There are 4 times as many vehicle accidents due to snow, sleet, icy, or blowing snow weather conditions as compared to those related to dense fog. However, the number of people killed in snow/sleet/icy weather conditions is only twice the deaths attributed to dense fog. Consequently, on a proportional basis, dense fog conditions are more deadly in Wisconsin.

Below is a table showing the average yearly number of reported vehicle accidents in Wisconsin associated with certain weather conditions... and the corresponding number of deaths and injuries /1988-99/...

Average Yearly:
Weather Conditions Accidents Deaths Injuries
Snow/Sleet/Ice/Blowing Snow 12,000 50 4500
Rain 10,000 45 5000
Fog 2,000 25 1000
An average of 135,000 vehicle accidents are reported each year in Wisconsin

Although the numbers in the table are considered "indirectly-related to actual weather conditions, they far exceed the number of people injured or killed due to tornadoes, flash floods, or lightning! It is not uncommon to read about multiple-vehicle accidents after several cars or trucks plowed into each other. Sadly, many of these weather-related accidents can be prevented.

Law enforcement officials and the insurance industry claim that most accidents that occur in fog are a result of motorists following too close to the vehicle ahead of them, and driving too fast for the weather conditions. The poor visibilities don/t allow motorists to make adjustments when the vehicle in front stops or makes a quick turn.

The State Patrol offers these safety tips while driving in dense fog
  • Headlights should be on low beam. This allows other drivers to see you.
  • Yellow fog lights are also helpful because they have less glare.
  • Motorists should drive slower and allow for extra time in reaching destinations.
  • Motorists should increase their following distances behind the vehicle in front.
  • Always assume there could be stopped traffic in front of you.

The NWS and State Emergency Management offer these additional tips
  • Listen to the latest forecast on NOAA Weather Radio, or commercial radio or TV or cable TV before leaving on your road trip.
  • Postpone your road trip when dense fog is forecast to reduce visibilities to near zero.
NWS Coordination Meteorologists Serving Wisconsin
URL: http://www.crh.noaa.gov/mkx/flyers/fog.php
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