SCOOT

Some Toronto intersections use a technology known as SCOOT - short for Split, Cycle and Offset Optimization Technique. It's a sophisticated program that is not only able to measure the ebb and flow of traffic, but even factor in accidents or stalled cars, so that lights at major intersections are adjusted accordingly.

It's able to respond by the second or the time of day, which is why the lights stay red longer at some parts of the morning or afternoon than they do at other times.

Toronto has had it in place at some selected corners since 1992, joining other large cities worldwide, including London, Santiago, Chile and Beijing.

If you're not at the intersections where it's installed, you're at the mercy of some bad timing.

At least one expert thinks we can't wait to change that.

"Toronto obviously is one of the worst in Canada in terms of terms of traffic flows and congestion," suggests U. of T. professor Bahir Abdulhai. "We're not as bad as California or Manhattan, but we are playing in the big leagues of congested cities."

Studies show the system works, cutting congestion, delays, pollution and even accidents by considerable margins.

SCOOT costs $20,000 for each intersection. Currently 315 of the City of Toronto's 1,900 signalized intersections hav SCOOT technology. It would cost approximately $32 million to install SCOOT at all of Toronto's signalized intersections. This is recommended as it would synchronize traffic lights and improve traffic flow.

SCOOT technology is installed at these locations:

Lakeshore East from the Don Roadway to Windermere Ave.
Black Creek Drive from Lawrence to Weston
The Queensway from The West Mall to Colborne Lodge
Bayview from Steeles to Moore Ave.
Eglinton East from Leslie to Cedar Rd.
Don Mills Road from Steeles to Overlea Blvd.
Dundas from Neilson to Aukland Rd.
Steeles from Yonge to Kennedy Rd.
Yonge from Steeles to Mill St.
Avenue Road from 401 westbound off ramp to Chaplin Cr.
Bloor St. from Avenue Road to Castle Frank Rd.
Eglinton West from Royal York to Hwy. 27
Lawrence W. from Bolingroke Road to Shermount Ave.

Sheppard Ave. Cluster

Beecroft Road and Sheppard Ave.
Yonge and Sheppard Ave.
Doris and Sheppard Ave.
Bayview and Sheppard Ave.
Barberry Place and Sheppard Ave.
Hawksbury Dr. and Sheppard Ave.
Don Mills and Sheppard Ave.
Parkway Forest Drive and Sheppard Ave.
D.V.P. West Ramp and Sheppard Ave.
404 Ramp and Sheppard Ave.

Downtown Core

Bay St.
Church St.
Charles St.
Davenport Rd. 
Grosvenor St.
Isabella St.
Jarvis St.
Sherbourne St.
Wellesley St.

How much of a difference does SCOOT make? According to a Toronto study, here's the impact:

• Traffic Flow Speeds: Increased 3% to 16%
• Left Turn Violations: Reduced 71%
• Rear-end Conflicts:  Reduced 24%
• Ramp Queues: Reduced 14%
• Intersection Stop: Reduced 18% to 29%
• Intersection Delays: Reduced 10% to 42%
• Left Turn Delays: Reduced 0% to 35%
• Vehicle Delay: Reduced 6% to 26%
• Vehicle Stops: Reduced 10% to 31%
• Vehicle Travel Time: Reduced 6% to 11%
• Pollution Emissions: Reduced 3% to 6%
• Fuel Consumption: Reduced 4% to 7%

Transit Effects

Travel Time

• In the AM peak period, round trip transit travel time was reduced by 34 seconds (2%)
• In the midday period, round trip transit travel time was reduced by 84 seconds (6%)
• In the PM peak period, round trip transit travel time was reduced by 69 seconds (4%)

Signal Delay

• In the AM peak period, round trip transit signal delay was reduced by 61 seconds (30%)
• In the mid-day period, round trip transit signal delay was reduced by 74 seconds (40%)
• In the PM peak period, round trip transit signal delay was reduced by 79 seconds (37%)
  

Courtesy: Intelligent Transportation Systems (ITS) 

SCOOT technology diagram


The operation of the SCOOT model is summarised in the diagram above. SCOOT obtains information on traffic flows from detectors. As an adaptive system, SCOOT depends on good traffic data so that it can respond to changes in flow. Detectors are normally required on every link. Their location is important and they are usually positioned at the upstream end of the approach link. Inductive loops are normally used, but other methods are also available.

When vehicles pass the detector, SCOOT receives the information and converts the data into its internal units and uses them to construct "Cyclic flow profiles" for each link. The sample profile shown in the diagram is colour coded green and red according to the state of the traffic signals when the vehicles will arrive at the stopline at normal cruise speed. Vehicles are modelled down the link at cruise speed and join the back of the queue (if present). During the green, vehicles discharge from the stopline at the validated saturation flow rate.

The data from the model is then used by SCOOT in three optimisers which are continuously adapting three key traffic control parameters - the amount of green for each approach (Split), the time between adjacent signals (Offset) and the time allowed for all approaches to a signalled intersection (Cycle time). These three optimisers are used to continuously adapt these parameters for all intersections in the SCOOT controlled area, minimising wasted green time at intersections and reducing stops and delays by synchronising adjacent sets of signals. This means that signal timings evolve as the traffic situation changes without any of the harmful disruption caused by changing fixed time plans on more traditional urban traffic control systems.