Traffic Signals Systems
Computerized traffic control signal systems are used to view and manage current traffic conditions, diagnose signal system problems and implement or modify signal timings remotely.
The City operates the two computerized traffic control signal systems.
TransSuite Traffic Control System (TransSuite TCS)
TransSuite TCS is a hybrid traffic control system that relies on second-by-second communication to monitor signal operations, but relies on field equipment to maintain coordination (i.e. the field equipment can maintain signal coordination for about 24 hours if there is a loss of communication). TransSuite TCS does not directly control signal movements, but commands each intersection controller to follow a timing plan that resides within its local database. TransSuite then verifies that the controller adheres to the commanded timing plan. Intersection controllers are monitored and controlled through a user interface. TransSuite TCS supports a variety of phase-based controllers.
Split Cycle Offset Optimization Technique/Urban Traffic Control (SCOOT/UTC)
SCOOT is an adaptive traffic control system that determines its traffic timing plans based on real-time information received from vehicle detectors located on the approaches to signalized intersections. Like MTSS, SCOOT relies on telephone communication to maintain signal coordination. UTC is a traffic control system that operates in tandem with SCOOT; it also relies on telephone communications. UTC provides pre-determined signal timing plans and is used as a stop gap measure if SCOOT is not available. SCOOT signals are sometimes called “smart” signals.
Mode of Control (MOC) refers to the type of traffic signal operation at signalized intersections. Toronto determines the MOC for existing signals based on current off-peak pedestrian and vehicle volumes. Toronto determines the MOC for planned signals based on projected off-peak pedestrian and vehicle volumes. The City uses the following modes of control: fully-actuated (FA), fixed-time (FXT), semi-actuated (SA), semi-actuated pedestrian (SAP), semi-actuated vehicle (SAV), and pedestrian-actuated (PED). View the map and list showing the mode of control for all signals in Toronto.
Fully Actuated (FA)
FA is a signal operation with stop-bar presence (intrusive or non-intrusive) detectors and push-buttons on all approaches; vehicles and pedestrians can receive different times; vehicle extensions; pushbutton activation required for “Walk” display; signal can rest on any phase by time-of-day.
Fixed Time (FXT)
FXT is a signal operation in which the vehicle signal indication changes automatically from the main street to the side street, and back, even if there are no vehicles on the side street and/or no pedestrians wishing to cross the main street. There is no vehicle detection on the through phase(s), and except at Accessible Pedestrian Signal locations, there are no pedestrian pushbuttons.
SA is a signal operation in which signals will not change to the side street unless a vehicle or pedestrian has been detected. Side street signal display and vehicle green time varies depending on whether a pedestrian call has been received or not. Pushbutton activation is required for the “walk” display. Demand on a vehicle presence detector actuates the vehicle green display; the “don’t walk” display will continue to be displayed for pedestrians. Vehicles receive a minimum green time. If there is continued vehicle presence on the detector, the side street green time can be extended to a predetermined maximum value. Demand on a pedestrian pushbutton actuates both the vehicle green display and the “walk” display for the pedestrian minimum green time, followed by a “flashing don’t walk” display for pedestrians, while the vehicle green continues to be displayed.
Semi-actuated Pedestrian (SAP)
SAP is a signal operation in which signals will not change to the side street unless a vehicle or pedestrian has been detected, and in which the side street will serve the pedestrian “walk” phase regardless of whether or not a pedestrian call has been received. Pushbutton activation is not required for the “walk” display if a vehicle is present. Demand on either a vehicle presence loop detector or a pedestrian pushbutton will actuate both the vehicle green and pedestrian “walk” display. Vehicles and pedestrians receive the same amount of time regardless of the actuation source. There are no vehicle extensions.
Semi-actuated Vehicle (SAV)
SAV is a signal operation in which there is no pedestrian crossing across the main street and there are no pushbuttons. Continued vehicle demand on a vehicle presence loop detector extends the vehicle green display up to a predetermined maximum value.
Pedestrian Actuated (PED)
PED is a signal operation where the mid-block pedestrian crossing is actuated by a pedestrian pushing a button. It provides pedestrians with a protected crossing opportunity by requiring motorists to stop at the signal.
Traffic signals are a vital tool used to safely and efficiently manage vehicle, bicycle and pedestrian traffic on City roads. City staff conduct traffic signal a warrant analysis to determine whether traffic signals should be installed at an existing intersection or at a mid-block location. The traffic signal warrant analysis follows the seven justifications outlined in the province’s Ontario Traffic Manual (OTM) Book 12 (2012), with the exception of Justification 4 which is omitted.
Amber and all-red durations or vehicle clearances, in the form of amber (yellow) and all-red clearances are provided at all signalized intersections in the City of Toronto. Vehicle clearances are calculated based on the guidelines stipulated in the Ontario Traffic Manual (OTM).
The duration of the amber display ranges from three to five seconds. An amber display is provided before every all-red signal display. The onset of the amber display indicates that the right-of-way is about to change and motorists should be prepared to stop. The duration is dependent on driver reaction and perception time, vehicle speed, average vehicle deceleration rate and the grade (slope) of the roadway. Generally, the amber durations are:
- posted speed of 70/km/h – five seconds
- posted speed of 50 and 60 km/h – four seconds
- posted speed of 30 and 40 km/h – three seconds
Intersections with a steep downgrade can have a slightly longer amber duration because vehicles on the downgrade can take a longer time to decelerate and come to a stop. Intersections with a steep upgrade can have a slightly shorter amber duration because vehicles on the upgrade can take a shorter time to decelerate and come to a stop.
The duration of the all-red display ranges from two to four seconds. An all-red display is provided after every amber signal display. The all-red duration provides a safe passage for vehicles entering the intersection at or near the end of the amber interval. The all-red duration is dependent on the vehicle crossing distance, the length of the average passenger vehicle and the approach operating speed. Generally, the vehicle crossing distance is based on the intersection width, the length of the average passenger vehicle is 6.0 m and the approach operating speed is the posted speed limit.
Inoperative traffic control signals, caused by a power outage, show themselves as blank (or dark) vehicle and pedestrian signal heads. In such situations, the driver must treat the signalized intersection as an all-way stop.
Some signalized intersections are equipped with battery backup-up systems (also called uninterruptable power supplies or UPS) which provide standby power for a limited period. UPS systems consist of an enclosure or cabinet, the batteries, the power inverter/conditioner, a battery charger (usually integral to the inverter), and automatic and manual bypass switches. These traffic control signals will operate normally for a six to eight hour period. If the power disruption continues, the traffic control signals will go into a red-red flash mode for an additional four to six hours. After that additional period, the signal indications will be dark and the intersection must be treated as an all-way stop.
Installing UPS systems at locations where there have been power issues helps reduce downtime and electrical damage to equipment. For example, a signalized intersection that is equipped with a UPS can continue to operate through short-term power losses. Generally, UPS are installed at:
- traffic control signals interconnected with light rail transit (LRT) systems
- traffic control signals with railroad pre-emption
- traffic control signals with advanced warning flashers (AAWF)
- traffic control signals at ramps from expressways
Getting to the scene of a fire or another emergency situation as quickly and safely as possible means saving lives. That’s the reason the City of Toronto has put in place a system to allow the fire division to temporarily affect traffic lights in order to get to an emergency even faster.
It works this way. A push button, which activates the traffic signal, is located in the radio room or in the truck bays at the fire hall. Once activated, the traffic signals are programmed to allow emergency vehicles to move quickly and safely on their way. In all, 50 traffic control signals are equipped with these circuits. These signals are located at either fire station exits or close to the stations. Once the emergency vehicles have passed through the traffic signals, the traffic lights return to their regular sequence.
A similar program is in place to allow TTC vehicles to move more effectively around the city. Transit vehicles are detected as they approach an intersection by antennas embedded in the pavement about 50-250 metres in front of the intersection. This allows a signal controller to make a change to the signal to allow the transit vehicle to proceed more efficiently.