Wires beneath the pavement gather information about traffic flow and average speed, relaying that information to a Traffic Operations Centre through fibre optic and coax cables. That information, processed by a special computer program, is displayed on screens in front of operators who are also watching live visuals from closed circuit television cameras located every kilometre or so along the freeway. In addition, information is called in by maintenance staff patrolling the freeways.
All of this information is used to dispatch appropriate emergency response vehicles or teams to the scene of incidents that are slowing or otherwise impeding traffic flow. Motorists are informed through computer-generated messages displayed on signs at strategic division points along the freeway.
This is all part of COMPASS, a high-tech traffic management system designed to reduce traffic congestion and improve safety by allowing the prompt detection and removal of vehicles obstructing traffic flow, managing peak rush hour traffic flow and providing accurate and timely information to motorists. Similar systems are in use in the United States, Europe and Asia.
The Mississauga COMPASS system, installed on the QEW between Erin Mills Parkway and Hurontario Street in 1975 was the first in Ontario. That system was closed and the equipment and information integrated into the Burlington system which had been installed in 1986. The first leg of the Toronto COMPASS system was installed on the 16-km section of the 401 between Yonge Street and Martin Grove Rd. in 1991. The Ottawa component was installed in 1997. Since then, the system has been expanded geographically to cover the entire section of the 401 within the Toronto region, and continually upgraded with new technology and software.
Inductance loops are embedded in the road surface, one per lane in most cases. In some locations, there are two loops spaced so that the system can measure average speed of the traffic flow. Called Vehicle Detection Stations (VDS), these loops are buried every 500-800 metres under the 401, on entrance and exit ramps, transfer roads and connecting freeways. They provide a continual stream of information on not only flow and speed, but spacing and volume.
The Closed Circuit Television (CCTV) cameras are spaced about one kilometre apart. They serve as a redundant and more visual confirmation of the data provided by the VDS system.
When the operations centre identifies a problem through these various systems, operators dispatch the appropriate response equipment - police, fire, ambulance or towing, or any combination. At the same time, the system provides messages to the message signs spread across the effected area. These same computerized signs can also automatically display real-time congestion information detected by the VDDS system.
In addition, information on traffic is relayed through other methods to a variety of public information outlets, primarily radio stations that are automatically sent a fax.
As of the end of December, the Toronto COMPASS system stretched from the Highway 401/QEW interchange to the 401/410 interchange and eastward to Harwood Avenue. Covering about 110 km, including some sections of adjoining highways it helps to manage traffic on Highways 401, 400, 403, 404, 424 and 410. Included are 93 CCTV cameras, 42 LED-type information screens, 761 Vehicle Detection Stations and more than 3,900 detectors.
The Burlington/Mississauga system has 92 cameras, 12 message signs, 280 detection stations and is unique in that it is interconnected to the liftbridge on the parallel road and Eastport Drive so the bridge operator can alert motorists and allow bypass decisions.
The Ottawa COMPASS system has 15 cameras positioned along 21 km of Highway 417 between Highway 416 in the West and Regional Road 174 in the east.