Turning movement counters

Turning movement counters (TMC's) are devices used to manually encode turning movement counts, a standard way of quantifying the movement of people and vehicles through an intersection.

Device for manually recording a turning movement count

TMC's are square shaped boxes that have buttons for each direction of traffic flow. For example, east bound traffic entering an intersection has a button for those vehicles that turn, left, right or continue straight. Furthermore, an additional button is used for each direction to add the number of pedestrian and bicyclist movement. Typically automated traffic counters assess traffic flows, however, due to the differing angles of vehicles entering an intersection the present technology available is not able to quantify the traffic without major error. Traditional automated traffic counters have rubber tubes which are laid out across the road generally in a straight portion in order to have the wheels on the same axle hit at about the same time. When turning in an intersection the tires hit individually and the amount of error in the counter is increased. This means that TMC's are the only present option for quantifying traffic flows. They are used manually by an individual pressing the correlating button for every vehicle that enters and moves through the intersection.

References

• Murthy, Narasimha & Henry R. Mohle. "Transportation Engineering Basics", ASCE Press