The impact of the February 1-2, 2011, storm on highways in Illinois was significant. Using snowfall data and Illinois DOT highway data, our GIS specialist Zoe Zaloudek was able to calculate the number of miles of interstate, US highways, and state roads covered by selected amounts of snow.
Below is the resulting map showing both the roads and significant snowfall. A table at the bottom of the map shows the number of miles affected by 6, 8 and 12 inches or more of snow. The impacts were felt all the way from Quincy to Chicago. We chose a starting point of 6 inches as the threshold for significant disruption of traffic and higher removal cost, based on earlier studies in Illinois.
For example, about 1,132 miles of interstate roads in Illinois received 12 inches or more of snow. Including 1,762 miles of US highways and 4,099 miles of state roads, it adds up to an incredible 6,993 miles of roads with a foot or more of snow to plow.
These estimates do not include the thousands of miles of county roads as well as city streets and alleys in the Chicago metropolitan area and elsewhere. However, we did not have a complete database of those road systems. Also roads covered by less than 6 inches of snow were treated as well for additional costs.