Press the yellow button and the 200-tonne train starts to roll. It drives itself, double-checking its position along the way and keeping to the correct speed for each stretch of track. At the next station it slows itself, then comes smoothly to a stop.

It really is that easy.

A subway operator sits behind the new controls. With the push of a yellow button, the train starts to move.

The Toronto Transit Commission is in the midst of a transformational shift to automatic train operation, a $563-million project that promises greater safety, improved efficiency and increased passenger capacity. When it starts to roll out this fall, the system – which will still include on-board staff in case of emergencies – will allow the agency to run many more trains per hour.

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The new system is "like autopilot on an aircraft," said project manager Pete Tomlin, a veteran of similar signal upgrade jobs in London and Hong Kong.

In the best-case scenario, TTC staff say, they could run about 32 trains per hour when the system is fully operational. That remains an ambitious goal – and will depend on time spent in stations, crew changes and turnaround times at the ends of the line – but one that would represent a huge increase over the current maximum of about 25.

Getting to that future is a mammoth task, made more difficult by the fact that the work has to be done around the demands of the country's busiest subway line. Finishing the first phase of the new system – the stretch from Dupont to Yorkdale stations that is being done now – requires 262 beacons, 23 signals, 78 kilometres of cable and 3,150 splices. And all of it has to be installed when the subway is closed.

Getting it installed and dialled in perfectly is a long process – and the reason for the ongoing series of weekend subway shutdowns on the Yonge-University-Spadina (YUS) line. During one of these shutdowns earlier this spring, The Globe and Mail got a rare chance to go behind the scenes to see the operation.

Video Take a look inside the TTC’s overhaul of the Yonge-University-Spadina subway line 3:30

Expected completion dates of signal upgrades, by phase

Once past the doors of the shuttered section of subway, it was a beehive of activity. With all they needed to keep working underground for hours – there was even a small espresso machine – the crews deployed technology ranging from lowly strips of duct tape to highly sophisticated computing power.

By the time the system rolls out, the trains will look – to riders at least – like the current set-up. All of the minutiae will be fine-tuned before any paying customers get on board.

The TTC's current signalling system is called fixed-block. It divides the tunnel into sections and requires that each train keep at least one full section of tunnel between it and the next train. That large buffer keeps trains well apart, which reduces the number that can be put through the tunnel.

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FIXED BLOCK SIGNALLING In a fixed block system, the track is divided into “blocks.” The status of these blocks is shown along the track using signals similar to traffic lights How it works 1 Green means the block ahead is not occupied and the operator may proceed 2 Red means the block ahead is occupied. The axle needs to be in the block for the entire block to be considered occupied. Trainstop a stops a train by raising a trip arm if it fails to stop at a red signal 3 This system cannot determine the exact location of a train within a block, so additional blocks must be used as a buffer zone to ensure safe distance between trains 4 The following train must proceed slowly or stop until the two or more blocks ahead becomes clear, leading to large gaps between trains and slow service

The new system is called communications-based train control (CBTC) and establishes a variable buffer around each train – longer at high speed, shorter when moving slowly. When a train is motionless, the one behind will creep up to within 70 metres. But when moving at regular speed, they will keep a preordained 397 metres apart.

This variability lets them run more closely together while still keeping the requisite distance for safety. It is this new system that allows automatic train operation.

COMMUNICATIONS-BASED TRAIN CONTROL (CBTC) CBTC systems allow for trains to operate closer to one another without increasing risk by allowing them to communicate their precise location on a track How it works 1 The train’s location is determined by the ATC beacons a backed up by axle counters b along the tracks, and onboard controllers b. As a train passes over a beacon, the onboard controllerc communicates with it via antenna d. From there, Data Communications System antennas e transmit the information about speed, location and braking distance to the Trackside Radio Equipment f 2 The information is passed from the Trackside Radio Equipment to TTC's Transit Control Centre where all train movements throughout the system are coordinated 3 Data from each train is processed by the central computers; movement authorities and limits for each train are issued by the central computers which allow for real-time adjustments of speed and braking to allow for safe train separation while allowing trains to get closer to each other. This equates to increased capacity and thus reduced wait times between trains. MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: TTC

New York is currently undergoing protracted efforts to upgrade to CBTC. London has recently been doing the same, a process that will allow the Victoria line to operate as many as 36 trains per hour.

Although the TTC won't hit that number, the new system promises to add capacity while whittling away at signal-related delays. Signal problems coming during rush hour, when the system is heavily loaded, are particularly galling. They affect tens of thousands of people and have a knock-on effect across the broader city. On the YUS line, such signal-related delays averaged about 800 minutes in each of the past five years.

Even though the full benefits of the new technology won't be seen until it has been installed on the whole length of the YUS, Mike Palmer, the TTC's chief operating officer, said that having it even in portions will allow the subway to run more efficiently. A similar upgrade on the Bloor-Danforth line is expected to follow but is currently unfunded.

The agency plans to start rolling out automatic train operation within months, including on the new subway extension to Vaughan. The first phase of the work is scheduled to be done by September, with the whole line fitted with the new technology by 2019.

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From TTC’s transit-control centre, operators test the new signalling system in operation.

The TTC says its old signalling system, which dates to the 1950s and 1960s, is still safe, but it’s less efficient than the new one being introduced.

Mike Palmer, the TTC’s chief operating officer, is shown near some of the new signalling equipment.

Installation and testing are usually invisible to outsiders. On the same day as The Globe's visit, three young women who somehow found their way into a closed subway station early Saturday morning, after what appeared to have been a long night, were quickly sent packing. For everyone else, the only outward sign of anything unusual was that motorists driving on the Allen Expressway might have registered the slightly surreal sight of a train running northbound on the southbound track.

But the system is abuzz with activity during these times. A large crew was at work in the closed section of subway line, a group of them in charge of running test trains.

Key tasks included checking how precisely the trains stopped – which is where the duct tape came in handy – how well they stuck to the correct speed and how long they took to travel from station to station. Subsequent trials have included "rabbit tests" – running two trains in quick succession, one behind the other.

These trains look the same as the ones with which regular riders are familiar. Under the skin, though, the way they run is going much more high-tech. Near the front, on the wall separating the operator from the passengers, a nondescript panel hides the train's nerve centre. It is the "car-borne controller" that gets the signal when the yellow button is pushed and starts the train moving. It deals with all the systems on the trains and communicates with the outside world.

An opened panel shows the train’s onboard computer at work.

As the train rolls down the tunnel, it counts each wheel revolution, allowing the train to measure its progress along the track. Every 200 to 400 metres is a beacon that the train recognizes as it rolls over it, confirming it is where it thinks it is. Speed is regulated by the computer, trying to match as closely as possible the programmed instructions for that specific part of the system.

"There are far fewer moving parts at track level," Mr. Palmer said. "We're installing less equipment. There's more redundancy, there's more resilience."

At the same time, information is flowing between the train and the nearest of 19 rooms scattered through the system, bouncing between a pair of antennae on the train and others in the tunnels. And signals are also pinging back and forth between these rooms and the centrally located zone control operation, which keeps watch on all the trains in the system to make sure they're in the right place relative to each other.

"You have one desk that will be able to signal the whole line. So we load the schedule, and if nothing else happened and every train was on time in turn, the man or woman sitting here would do nothing," Mr. Palmer said in the zone control room.

"As soon as we deviate from the norm, this person will intervene. They can stop the train [remotely], they can [emergency brake] the train. If we want to turn a train … we say to the database, turn this train at St. Clair West. So when that train gets to St. Clair West it [goes], 'Oh, I'm turning here.'"

The whole Yonge-University-Spadina line is due to be fitted with the new technology by 2019.

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