Loops: This detection type involves multiple 6-foot by 6-foot wire coils (loops) installed under the road surface. When a vehicle drives over the loops, a vehicle detector is activated and sends a message to the traffic signal to change the signal accordingly. Loops are the oldest form of traffic detection and are no longer installed with new signals because they require drivers to stop in a specific area, don’t work well for motorcycles or bicycles, and are often destroyed by excavation or roadway deterioration.
Video detection cameras: These cameras are mounted for each approach to an intersection, and when they detect a vehicle, the signal will change. Cameras were installed in Missoula from 2001 until 2012 but are no longer installed because they can be affected by the sun and other light glare, fog, smoke, and build up on the lens from blowing snow and dirt.
Radar: The newest and best option for vehicle detection at this time is radar because it accurately detects all roadway users and is reliable.