WILLMAR -- If you've driven on one of Willmar's main streets recently, your vehicle was likely counted by the Minnesota Department of Transportation.
MnDOT is required by the federal government to conduct traffic counts every two years on trunk highways, such as U.S. Highway 12, and every four years on state-aid city streets and state-aid county roads.
This year is Willmar's year to be counted. Willmar was last counted in 2006, said City Public Works Director Mel Odens.
The data collected by the counts are used, among other things, for traffic planning purposes, signal analysis, and watching for route congestion, he said. Also, businesses moving to or expanding in Willmar are interested in traffic volume near their site.
"It's a good resource that the DOT does for us,'' said Odens. "If they didn't do it, we would have to do it ourself.''
State-aid city and county routes in Willmar include First Street, Willmar Avenue, Trott Avenue and Lakeland Drive. The downtown is also counted.
MnDOT's District 8 headquarters in Willmar conducts roughly 800 to 875 counts a year throughout the 12-county district. Kandiyohi County, which is part of the district, has 355 municipal and county road counts.
Counts are not conducted all on the same year but are spread out on a rotating basis.
"It spreads out the workload,'' says Randy Lindstrom, MnDOT transportation specialist and traffic count manager.
A counter is placed on a roadway for a 48-hour period. A vehicle is counted when it drives over a thin air-filled hose laid across the roadway. The hose is connected to a box secured to a post in the median or on the curb.
An air pulse caused by the tires crossing the hose activates a switch inside the box that counts the vehicle.
Counts begin in the spring and are completed in the fall. No counts are taken in the winter when plows are operating.
Lindstrom sends the data to MnDOT headquarters in St. Paul, which calculates the annual average daily traffic figure for each roadway.
State, county and city transportation agencies use the data for roadway design and funding purposes. Jon Henslin, MnDOT district traffic engineer, said funding formulas include the amount of lane miles and the amount of traffic.
"When you build that road, they'll look at the amount of traffic and that might make a difference between putting down 3 inches of bituminous or 6 inches of bituminous, depending on how much traffic they feel is going to be running over that surface,'' said Henslin.
Lindstrom and Henslin said MnDOT has conducted traffic counts for many years.
"We have a lot of history,'' said Henslin. "We can take a look at roads over a long period of time to see what's happening, which is very helpful. Normally we use this data to project forward 20 years. If we're doing some reconstruction, we'll watch what the trend line is and then project it out 20 years and say that's what we're designing for. We're designing for what the road will be like in 20 years.''