The Iowa Department of Transportation is counting cars once again this summer. The DOT sends counters to one quarter of the state each year — with the southwest area this year’s target.
Spokesman Mark Hansen says they use a combination of automated counters and real people, who give more detail of traffic movement. “The people at the intersection give us a turning movement. We actually know if a car is turning or going straight and that helps us with planning and engineering decisions,” Hansen explains.
The human counters also enter a description of the vehicle on a hand-held field computer. “With the manual counters, they are classifying the vehicles. They look at it if it is a passenger vehicle like a car or a pickup, versus a straight truck — a single unit is what we call it — and think of that as a UPS truck,” Hansen says. “And then we also classify the combination units, with are the semi trucks, tractor-trailer combination units.”
The DOT hires seasonal workers each year to conduct the count. He says they get a lot of college students who work the job during the summer, along with teachers and retirees. The manual counters go from 7 to 9 a.m., 11 a.m. to 1 p.m. and then 3 to 6 p.m. to hit the “rush” hour traffic each day. The automated counters add to the information gathered by the people.
“Recorders are set out sometime during the day — they either set there for 24 or 48 hours — and these are the black tubes that go across the roadway,” Hansen explains. “Depending on the traffic levels on the roadway, those people may put them out at midnight or even three o’clock in the morning…so if it is a very busy roadway, they are not setting them out at eight o’clock in the morning, for instance.”
The data gathered from both sources is used in determining the future development of roadways. “That information goes into our database, and then we can make planning and engineering decisions as far as: do we need a left turn lane here, do we need a stop sign, do we need signals, and even do we need to put a four-lane roadway in some instances,” Hansen says.
Hansen says moving around each year gives them numbers to compare. He says they can see the trends over the four years and make decisions, and if they need to they can also do a special count in areas if there is something unusual happening. Construction projects sometimes cause changed in traffic patterns and delay counts in some areas. Hansen says the counting can continue into September if needed.