SkyTrain station platform screen doors are unfeasible, says TransLink

Aug 23 2018, 5:51 pm

Transit systems in Canada’s two largest cities are increasingly looking to platform screen doors (PSD) as the solution to significantly improve safety and reliability levels of both train stations and operations.

PSDs are glass screens that provide a physical barrier between the platform and the train tracks. When trains arrive at a station, the train doors align with the PSD to allow for the egress and ingress of passengers.

The Réseau express métropolitain (REM) in Montreal – a brand new, $6.3-billion, 67-km-long automated SkyTrain-like train network with 26 stations – will open with PSDs for all stations when the system opens in 2021.

And earlier this summer, the Toronto Transit Commission announced it will be undertaking an engineering study to examine the feasibility of PSDs for its subway stations after a string of high profile deaths and injuries involving passengers falling into the tracks and into the path of a train. The highly preliminary cost estimate of retrofitting all subway stations for PSDs is $1 billion.

Such PSDs are common on train systems in Asia and increasingly in Europe, and they are also usually found on newer people mover systems at airports.

But for Vancouver’s SkyTrain system, the technology is still not feasible according to the local public transit authority.

Findings of a previous feasibility study

TransLink says its position on PSDs, since Daily Hive’s 2014 story on platform edge doors on SkyTrain, has not changed. As well, the problems outlined in a 1994 technical study on a potential retrofit of the then 20-station SkyTrain system with PSDs has not only remained constant but they have grown.

“From a purely technical perspective it would have been possible, but the trade-offs would have been too great even then rendering the concept impracticable,” TransLink spokesperson Jill Drews told Daily Hive. “Fast forward to 2018 and we have a much larger, more diverse SkyTrain system.”

Since then, the system has grown to three lines with 53 stations, various station design standards, and three generations of train cars.

The study had concerns over the different door spacings between the Expo-era Mark I trains and the incoming Mark II trains.

And with the new generation Mark III trains, the door spacing issue continues. The door size of the Mark III trains are the same as the Mark II trains, but the locations are different because the Mark III trains are slightly shorter and would result in a different door placement when stopped at the platform.

sustainable transit

The new generation Mark III SkyTrain car at Main Street-Science World Station. (Sounder Bruce / Flickr)

Wider PSDs to overcome the door placement issue were suggested as an option, but this would lead to safety and reliability issues due to the heavier weight of the PSDs and the need to have the doors overlap given that the distance between PSDs would be less than the PSD width. The distance between PSDs are usually emergency doors that open from the track side.

“Installing PSDs wide enough to fit all types would leave a large, dangerous gap between some trains and the PSDs,” said Drews.

Deep gaps between the trains and the PSDs can be fatal, as it creates a pocket space where passengers may become fatally trapped.

There have been instances on the subway systems in Beijing and Seoul where passengers try to force themselves onto a train while the PSDs are closing or they are pushed out of the doors of a packed train. When this occurred, the passengers found themselves trapped between the PSDs and the train doors. They were crushed to death when the train departed the station.

As for the installation process of the PSDs, it is much more complex than simply erecting the doors on the platform – especially for an existing train system.

The previous study listed the following required modifications:

  • Extension of outdoor station roof canopies to provide complete platform security and weather protection for the PSDs
  • Reconstruction of the station platform edges to create an anchor that can support the weight of the PSDs (although, some newer PSDs are floor-based and only reach the shoulder height of an average adult)
  • Modifications to the ceiling line to provide an anchor to the PSDs
  • Redesigning the ends of the station to include a full wall enclosure to provide restricted access to the tracks
  • New electrical power distribution systems
  • Modifications to ensure sufficient ventilation in the stations, especially underground stations that depend on the piston effect of train movement for air circulation
  • Consider possible greenhouse effect for outdoor stations
  • Modifications for the acoustic insulation in ceilings of underground stations
  • Modifications to SkyTrain’s automated train control system
  • Disconnection and removal of the existing platform and guideway intrusion systems
Screen Shot 2014-04-15 at 1.05.04 PM

Types of platform screen doors. (Westinghouse)

The construction work required to achieve these upgrades would be highly disruptive, with three options outlined.

One option would shut down the entire train line for an entire year, as it may be the most cost and schedule effective. An alternative to this option would be to shut down segments of the line, and transit riders would depend on a system of “bus bridges” between the closed sections.

A second option involves retrofitting the stations during the overnight non-operating hours while maintaining normal service options during revenue hours, which will take about 18 months. Certain recent and current renovation projects on SkyTrain, such as the Joyce-Collingwood Station platform retiling project and the rebuild of Metrotown Station, have proceeded using this method.

Another option involves the shutdown of individual stations while the doors are being installed and commissioned at that station. This third option is estimated to take up to 18 months.

“The report acknowledges that installation and construction would require service and station shutdowns for prolonged periods of time,” said Drews.

“We would be re-imagining the entire system which would cause a deep disruption to the system with massive impact on customers.”

The report estimated in 1994 that it would cost up to $68 million to retrofit the Expo Line with PSDs.

“Too much has changed to begin to estimate what it would cost to undertake a project like this now,” she said.

Copenhagen Metro platform screen doors

Platform screen doors on the Copenhagen Metro. (Shutterstock)

PSDs are far more common on brand new train systems where such equipment can be installed without any inconvenience, whereas significant disruptions to passengers are a major obstacle to overcome for existing systems.

The Hong Kong MTR subway was the world’s first train system already in operation to be renovated with PSDs. The full retrofit was completed in 2006.

Even Tokyo’s extensive subway system is not fully outfitted with PSDs; at the moment, the Tokyo Metro has 82 stations with PSDs – roughly 46% of the total number of stations. But Tokyo Metro Co. announced last year it has plans to install PSDs to another 50 stations in time for the 2020 Olympics, and work will continue in the years after with the installation of platform doors at the busiest stations with 100,000 or more passengers by 2024.

Five existing lines on the London Underground will also see PSDs over the coming years as part of the Deep Tube Upgrade Programme.

Clear benefits of platform screen doors

There is no question that platform screen doors have an immensely positive impact on service reliability and safety.

According to a case study, after the installation of platform screen doors on the MTR, “death and injuries due to suicides and accidental falls onto the track fell by 75% across the system and the service disruptions from such incidents fell by 69.4%.”

Currently, passengers are protected by SkyTrain’s platform and guideway intrusion systems, which is designed to detect foreign objects entering into the tracks from the platform level.

Kuala Lumpur MRT platform screen doors

Platform screen doors on the Kuala Lumpur MRT. (Shutterstock)

On the older Expo Line, metal plates on the tracks at the platforms act as track intrusion pressure sensors and are set to such a low tolerance that even objects as light as pop cans and newspapers will send the system to an immediate grinding halt.

The detection systems on the newer Millennium Line and Canada Line are more high-tech as they use an array of lasers and infrared sensors to detect intrusions.

As SkyTrain is a completely driverless train, these systems are key for operating and maintaining a safe system. Unfortunately, with this additional layer of safety unlike many other train systems, this also means many false alarms are frequent.

Severe injuries to passengers aboard cars is also a possibility if the track intrusion system is triggered just as a train arrives into the platform – it activates the approaching train’s emergency brakes, causing it to come to an abrupt skidding stop. This was the case on June 21, 2010, when a pop can fell onto the tracks. The sudden train stop sent three elderly women to hospital.

In May 2010, there were 231 track intrusion incidents – an average of about eight frequent disruptions to SkyTrain service per day. Of this number, 80 were the result of garbage falling onto the tracks and another 10 from people jumping into the tracks to retrieve their belongings.

Depending on the severity of the situation (false alarms, fallen belongings or a fatal incident), such disruptions cause systemwide service delays that last anywhere from several minutes to over an hour. The vast majority of the delays are false alarms from belongings and other objects falling onto the tracks and triggering the sensors.

Any track intrusion situation requires SkyTrain attendant presence to clear the tracks and provide control room operators with the green light to resume regular service.

Such intrusion sensor systems can be completely removed and replaced by PSDs.

Hong Kong MTR platform screen doors

Platform screen doors on the Hong Kong MTR. (Shutterstock)

At the same time, PSDs can also be responsible for delays, as the equipment is also occasionally prone to breaking from all of its moving parts. On the Expo Line, with trains arriving at stations as frequently as less than every two minutes, the PSDs would have to open and close hundreds of times each day.

For instance, in May 2018, a single faulty PSD at one Singapore subway station resulted in 45-minute-long travel delays over a 2.5-hour period during the evening peak rush. The Singapore MRT had to resort to running free bus shuttles between the affected stations.

For the time being, the largest technical obstacle with installing PSDs on Expo Line and Millennium Line is the varying train door placements of the Bombardier-designed trains. Although it is also important to note that the old Mark I cars will be gradually retired starting in 2026 and replaced with the Mark III.

But different door placements is not an issue for the Canada Line, which has one single model for its rolling stock of trains by Hyundai Rotem. Future additional orders of 12 two-car trains will be produced by the same South Korean company, and aside from slight interior design changes the model of train will be identical to the existing fleet.

Canada Line Waterfront Station SkyTrain

Crowds at the Canada Line’s Waterfront Station platform. (Daily Hive)

PSDs on the Canada Line would not only improve reliability and safety, but it would also provide a major boost to station capacity given the system’s short and narrow platforms, with most stations built to just 40 metre lengths. A handful of Canada Line stations, despite being about half the size, are far busier than most stations on the Expo Line and Millennium Line.

Future platform extensions to the ultimate design length of 50 metres to accommodate a third train car length could perhaps include retrofitting the stations to include PSDs.

But with a growing daily ridership now reaching 140,000 passengers per weekday, the only question is whether the users on the Canada Line are willing to put up with prolonged inconveniences caused by construction disruption.


See also
Kenneth ChanKenneth Chan

+ News
+ Venture
+ Transportation
+ Urbanized