Vehicle weights on County roads are dictated by the weight regulations established by the State of Illinois. All roads in Boone County have a maximum load weight of 73,280 pounds and a single axle weight load of 18,000 pounds. The only exception is Garden Prairie Road from U.S. Route 20 south to Garden Prairie Grain, a distance of approx. one half mile which is classified as a Class III truck route which allows a maximum vehicle load of 80,000 pounds.
Boone County also places a restrictive vehicle weight limit on the county highways in the spring when the frozen ground under the roads begins to soften. Although the time the postings are put into effect varies due to depth of frozen ground and air temperatures, the common period of the "spring postings " is mid-February to mid-April. All roads that do not have "spring postings " will not be issued over weight or over width permits during the days when the seasonal postings have been posted.