When a vehicle drives towards an intersection that has a traffic signal, these loops detect the presence of the vehicle and send a message to the control unit of the traffic signal that there is a vehicle approaching. This helps to reduce waiting time for the vehicle and avoids having the signal change if no vehicle is waiting. Pavement markings are sometimes made to rumble when vehicle tires across them. Ramp meters are traffic signals that use red and green signals to control how many vehicles enter the freeway. If too many vehicles enter the freeway at the same time during the rush hour, there is a dramatic slowing down of traffic and congestion throughout the freeway system.
Ramp meters regulate the flow of entering vehicles so that the vehicles can be accommodated.
By linking the ramp meters to the traffic signals in the area a steady, manageable flow of traffic can be maintained. Ramp meters help us use the existing transportation system efficiently and reduce the need for more freeways. Chemeketa Community College in Salem offers classes at the Transportation and Economic Development Center.