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.
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.
They are used manually by an individual pressing the correlating button for every vehicle that enters and moves through the intersection.