Platform screen doors

These doors help to:

• Prevent people from accidentally falling onto the tracks, getting too close to moving trains, and committing suicide (by jumping) or homicide (by pushing).[2]
• Prevent or reduce wind felt by the passengers caused by the piston effect which could in some circumstances make people lose their balance.
• Improve safety—reduce the risk of accidents, especially from trains passing through the station at high speeds.[2]
• Improve climate control within the station (heating, ventilation, and air conditioning are more effective when the station is physically isolated from the tunnel).[2]
• Improve security—access to the tracks and tunnels is restricted.[2]
• Lower costs—eliminate the need for motormen or conductors when used in conjunction with Automatic Train Operation, thereby reducing manpower costs.
• Prevent litter buildup on the tracks, which can be a fire risk, as well as damage and possibly obstruct trains.[3]
• Improve the sound quality of platform announcements, as background noise from the tunnels and trains that are entering or exiting is reduced.
• At underground or indoor platforms, prevent the air from being polluted by the fumes caused by friction from the train wheels grinding against the tracks.[4]

Their primary disadvantage is their cost; installing a system typically costs several million USD per station. When used to retrofit older systems, they limit the kind of rolling stock that may be used on a line, as train doors must have exactly the same spacing as the platform doors; this results in additional costs due to depot upgrades and otherwise unnecessary purchases of rolling stock.

The doors also pose their own safety risks. The primary risk is that people may be trapped between the platform doors and the train carriage, and be subsequently crushed when the train begins to move (see § Incidents). Cases of this happening are rare, and may depend upon door design.

• 
  Platform edge doors at Kwai Hing Station of Hong Kong MTR
• 
  Fully enclosed platform screen doors at Jiashan Road Station of Line 9 in Shanghai Metro
• 
  Fully enclosed doors at Ecological District Station of Kaohsiung MRT in Taiwan
• 
  Full-height platform screen doors at Castle Hill Station on the Sydney Metro

Half-height platform gates at Sunny Bay Station on the Disneyland Resort Line in Hong Kong

Half-height platform doors, or automatic platform gates, are chest-height sliding doors at the edge of railway platforms to prevent passengers from falling off the platform edge onto the railway tracks. Like full-height platform screen doors, these platform gates slide open or close simultaneously with the train doors.

Half-height platform gates are cheaper to install than platform screen/edge doors, which require more metallic framework for support. Some railway operators may therefore prefer such an option to improve safety at railway platforms and, at the same time, keep costs low and non-air-conditioned platforms naturally ventilated. However, these gates are less effective than full platform screen doors in preventing people from intentionally jumping onto the tracks.

These gates were first in practical use by the Hong Kong MTR on the Disneyland Resort Line for their open-air station design. The later design by other manufacturers, such as Manusa, Grupsa or Gilgen Door Systems AG, have their gates higher than the ones installed on the Disneyland Resort Line.

Line D of the Buenos Aires Subte is planned to have platform screen doors installed in the future as soon as the CBTC system is installed.[5][6][7]

Rouse Hill Station on the Sydney Metro

In Sydney, the first phase of the Sydney Metro (known as Sydney Metro Northwest) opened in May 2019, and was the first-fully automated rapid transit rail system in Australia. The stations are equipped with full-height platform screen doors on most underground platforms and half-height doors on at grade, elevated and some underground platforms. The existing five stations on the Epping to Chatswood railway line were upgraded to rapid transit standard, all featuring half-height platform screen doors.[8]

In Melbourne, the Melbourne Metro tunnel currently under construction from South Kensington to South Yarra will feature platform screen doors on the underground stations.[9] New trains are being constructed that will line up with the full-height doors. The Metro Tunnel is due to open in 2025.

Platform screen doors are being added to Line 3 of the Minsk Metro, which is due to open in late 2020. [10]

Paulista Station on São Paulo Metro's Line 4, the first fully automated transit line in Latin America.[11]

The Platform Screen Doors are present in the São Paulo Metro since 2010, when the Sacomã Station was opened.[12] As of 2019, 5 of the 6 lines of the São Paulo Metro have the equipment: Line 4 - Yellow and Line 15 - Silver have the equipment installed in all of its stations. The feature is also present in some stations of Line 2 - Green, Line 3 - Red and Line 5 - Lilac. They are planned to be installed in 41 stations of lines 1, 2 and 3 by the end of 2021[13], as well as all stations of line 5 by the end of 2020.[14]

PSDs are also found on Santos Light Rail since 2016.[15]

Half-height platform screen doors will be in use on all stations of the Sofia Metro Line 3.[16]

Screen doors are in use at all three LINK Train stations and the Union and Pearson stations along the Union Pearson Express route to Toronto Pearson International Airport in Mississauga, Ontario.

Greater Montreal's forthcoming Réseau express métropolitain (REM), the 67-kilometre-long driverless complementary suburban rapid transit network opening in three phases between 2021 and 2023 will feature screen doors at each of its 26 stations.

With the advent of the REM on the horizon, advocating retrofits of platform edges in the Montreal Metro with doors to combat delays attributed to overcrowding is becoming increasingly customary. Were its type of door to be screen (full-height), then such installations might quash the fully underground system's notoriety whereby opening or passing through station entrance doors proves mightily troublesome due to the excessive windiness brought about by arriving or departing trains.

Line 6 of the Santiago Metro, inaugurated in November 2017, introduced the platform doors and converted it into one of the most modern in Latin America

Platform edge doors are currently in use at Lines 3 and 6 of the Santiago Metro, being a novelty in the system.

All Chinese metro systems have platform screen doors installed on most of their lines. All stations built after the mid 2000s have some form of platform barrier. Only the Beijing Subway, Nanjing Metro, Dalian Metro and Wuhan Metro have stations without the platform screen doors on their early lines (As of 21 September 2019). However many are starting the process of retrofitting these lines with platform screen gates. In addition, many BRT systems such as the Guangzhou Bus Rapid Transit are also equipped with platform screen doors. Several underground high speed railway stations of the CRH network use platform screen doors set back from the platform edge.

The Copenhagen Metro uses Westinghouse[17] and Faiveley platform screen doors on all platforms.

The Helsinki Metro had a trial run with Faiveley automatic platform gates installed on a single platform at Vuosaari metro station during phase one of the project. The doors, which are part of the Siemens metro automation project, were built in 2012. Phase 2 of the project has been delayed due to metro automation technical and safety related testings.[18] The doors were removed in 2015

Fully enclosed platform screen doors in Paris Métro

All lines of the VAL automated subway system are equipped with platform screen doors at every station, starting with Lille subways in 1983. Those also include Toulouse and Rennes as well as the CDGVAL and Orlyval airport shuttles.

Paris Métro's line 14 from Saint-Lazare to Bibliothèque François Mitterrand was inaugurated in 1998 with platform screen doors manufactured by Faiveley Transport. The new station Olympiades opened with platform screen doors in June 2007. Line 1 has been retrofitted with platform screen doors, for full driverless automation effective in 2012. Some stations on Line 13 have had platform edge doors since 2010 to manage their overcrowding, after tests conducted in 2006, and stations on Line 4 are currently being fitted with platform edge doors in preparation for its automation.

The D line in Lyon, which is equipped with fully automated trains, does not have platform screen doors but identifies obstructions by infrared detectors upon the tracks. A similar system is employed by the metro system in Nuremberg, Germany.

People movers at Frankfurt International Airport, Munich International Airport and Düsseldorf Airport are equipped with platform screen doors, as well as the suspended monorail in Dortmund, called H-Bahn.

Platform screen doors will be used on the driverless Thessaloniki Metro[19], which opens in November of 2020.

East Tsim Sha Tsui Station has the longest set of platform screen doors in the world, but a third have been out of service since the station began serving the West Rail Line's shorter trains in 2009.

Today, all heavy rail platforms except those on the East Rail Line have either platform screen doors or platform edge doors. Platform edge doors are only used on above-ground stations, while platform screen doors are used in both underground and above-ground stations. None of the light rail platforms has platform screen doors or platform edge doors.

In 1998, the Tung Chung Line and Airport Express saw the earliest operations of platform screen doors in Hong Kong.

The MTR Corporation had also, since mid-1996, been studying the feasibility of installing PSDs at the older stations. It decided in 1999 to undertake the PSD Retrofitting Programme at 74 platforms of 30 underground stations on the Kwun Tong, Island, and Tsuen Wan Lines. This was completed in early 2006.[20] The Mass Transit Railway was the first metro system in the world to retrofit PSDs on a transit system already in operation.[21]

In 2006 the MTR began studying ways to introduce barriers at above-ground and at-grade stations, which was considered more complicated as these stations are naturally ventilated and the introduction of platform screen doors would entail the installation of air conditioning systems. In 2008 the corporation decided to install automatic platform gates at these eight stations (the MTR and KCR Corporation were operationally merged in 2007, but KCR stations were except from this study).[20] The eight stations were retrofitted with APGs in 2011.

From July 2000 to December 2013, the MTR Corporation collected a surcharge of 10 cents from each Octopus-paying passenger to help pay for the installation of PSDs and APGs. Over HK$1.15 billion was collected in total.[22]

Platform screen doors were also installed on all platforms of the West Rail Line, then built by the Kowloon-Canton Railway Corporation (KCRC) before the MTR-KCR merger. The Ma On Shan Line did not have gates upon opening even though it was built at the same time as the West Rail.

The installation of platform screen doors in Hong Kong has been effective in reducing railway injuries and service disruptions.[23]

The longest set of platform screen doors in the world can be found in East Tsim Sha Tsui Station.[24] A reduction of train length from 12 to 7 cars following the construction of Kowloon Southern Link caused many of the screen doors to be put out of service, although the trains were lengthened to eight cars in May 2018.

The platform screen doors presently in service in the MTR were supplied by the Swiss manufacturer Kaba Gilgen, the Japanese Nabtesco Corporation (under the Nabco brand), as well as Faiveley Transport. The last stations in Hong Kong without platform screen doors or gates are all found on the East Rail Line and Ma On Shan Line, both former KCR lines not part of the MTR APG retrofitting programmes. However, these remaining stations are all being retrofitted by Kaba as part of the Sha Tin to Central Link project.[25] Adding APGs to the East Rail platforms requires platform strengthening as the gates, combined with heavy winds, can greatly increase structural loading on the platform edge.

Apart from the MTR, all stations on the Hong Kong International Airport Automated People Mover are equipped with platform screen doors made from Westinghouse Platform Screen Doors (for Phase 1)[26] and Panasonic (for Midfield Extension).[27]

On the Delhi Metro, all stations on the Delhi Airport Metro Express line, which links to Indira Gandhi International Airport have been equipped with full-height platform screen doors since November 2015 and the six busiest stations on the Yellow Line have also been equipped with half height platform gates.[28][29] Automatic platform gates on all the stations of the Pink and Magenta Line.

Platform screen doors are also used in all underground stations of the Chennai Metro.[30]

There are platform screen doors in all elevated stations of Kolkata Metro Line 2. Platform screen doors will be introduced in underground stations of Kolkata Metro Line 2, Kolkata Metro Line 3, Kolkata Metro Line 6. There are plans to install platform screen doors also in Kolkata Metro Line 1.[31]

On the Namma Metro in Bangalore, platform doors will be installed for its phase II operations and is expected to be completed by 2019.[32]

• 
  Full-height platform screen doors installed in Chennai Metro's underground stations
• 
  Half-height automatic platform doors in Okhla Bird Sanctuary Station of the Delhi Metro's Magenta Line.

Platform screen doors are in use on the underground stations on the new Jakarta MRT and half-height doors are used on above-ground stations. Soekarno–Hatta Airport Rail Link stations, such as SHIA railway station, also uses platform screen doors. The Jakarta LRT also uses half-height doors at its stations (all above ground). The TransJakarta bus rapid transit system also uses automatic half-height doors at the Bundaran HI and Tosari stations. In the future, platform screen doors and half height doors will be installed on Phase 2 and 3 of the Jakarta MRT.[33]

• 
  Platform screen doors at one of SHIA Skytrain station
• 
  Platform screen doors at SHIA railway station
• 
  Platform screen doors at Bundaran HI MRT station
• 
  Half-height doors at ASEAN MRT station
• 
  Half-height doors at TransJakarta Bundaran HI station

Platform screen doors at the Monte Compatri-Pantano station on Rome Metro's Line C

Platform screen doors are used in most newly built rapid transit lines and systems of new construction in Italy. PSDs are present on Turin Metro, the Venice People Mover, the Perugia Minimetrò, the Brescia Metro, Line 5 of the Milan Metro, and Line C of the Rome Metro.

Full-height doors on Tokyo Metro Namboku Line and Toei Mita Line

The Tokyo Metro and Toei Subway began using barriers with the 1991 opening of the Namboku Line (which has full-height platform screen doors), and subsequently installed automatic platform gates on the Mita, Marunouchi, and Fukutoshin lines. Some railway lines, including the subway systems in Sapporo, Sendai, Nagoya, Osaka, Kyoto, and Fukuoka, also utilize barriers to some extent.

In August 2012, the Japanese government announced plans to install barriers at stations used by 100,000 or more people per day, and the Ministry of Land, Infrastructure, Transport and Tourism allotted 36 million yen ($470,800) for research and development of the system the 2011-2012 fiscal year. A difficulty was the fact that some stations are used by different types of trains with different designs, making barrier design a challenge.[34]

As of November 2012, only 34 of 235 stations with over 100,000 users per day were able to implement the plan. The ministry stated that 539 of approximately 9,500 train stations across Japan have barriers. Of the Tokyo Metro stations, 78 of 179 have some type of platform barrier.[35]

In 2018, automatic platform gates will be installed on the Sōbu Rapid Line platforms at Shin-Koiwa. As these trains are 300 m (980 ft) long, it is believed that this will break the world record for the longest platform doors at East Tsim Sha Tsui Station in Hong Kong.[36][37]

Platform screen doors (PSD) are installed at all underground Kelana Jaya Line stations, from Ampang Park to Masjid Jamek and Kajang Line, from Muzium Negara to Maluri stations. The automated announcement message reading "For safety reasons, please stand behind the yellow line" in both English and Malay languages are also heard before the train arrived at all stations.

There are also platform screen doors (PSD) on the KLIA Ekspres at Kuala Lumpur Sentral and KLIA stations. Both stations at KLIA Aerotrain also have platform screen doors.

The Platform screen gates (PSG) also have been installed in all elevated stations of the Kajang Line and KL Monorail.

• 
  PSD at KLCC station
• 
  PSD at Tun Razak Exchange station
• 
  PSD at Kuala Lumpur International Airport ERL station
• 
  PSD at KLIA Satellite A Building
• 
  PSG at Semantan station

In Pakistan, platform screen doors are installed at all stations of bus rapid transits Lahore Metrobus and Rawalpindi-Islamabad Metrobus. There are plans to install them at all stations of Multan Metrobus, Karachi Metrobus and the under construction Lahore Metro.

Platform screen doors are in use in all stations of the Doha Metro. [38]

Park Pobedy (Russian: Парк Победы) is a station of the Saint Petersburg Metro that was the first station in the world with platform doors. The station was opened in 1961. Later, nine more stations of this type were built in Leningrad (nowadays Saint Petersburg): Petrogradskaya (Russian: Петроградская), Vasileostrovskaya (Russian: Василеостровская), Gostiny Dvor (Russian: Гостиный двор), Mayakovskaya (Russian: Маяковская), Ploshchad Alexandra Nevskogo I (Russian: Площадь Александра Невского-1), Moskovskaya (Russian: Московская), Yelizarovskaya (Russian: Елизаровская), Lomonosovskaya (Russian: Ломоносовская), and Zvyozdnaya (Russian: Звёздная).

There was an electronic device to ensure that the train stopped with its doors adjacent to the platform doors; they were installed so that driverless trains could eventually be used on the line.[39] Unlike other platform screen doors, which are lightweight units with extensive glazing installed on a normal platform edge, the St Petersburg units give the appearance of a solid wall with heavyweight doorways and solid steel sliding doors, similar to a bank of elevators in a large building, and the train cannot be seen entering from the platform; passengers become familiar with the sound alone to indicate a train arrival.

In May 2018, two other similar stations were opened: Novokrestovskaya and Begovaya. Unlike the first ten stations that were built, these stations utilize glass screen doors, allowing the train to be seen from entering the platform.

• 
  Hall of Begovaya station
• 
  Hall of Petrogradskaya station

The Singapore Mass Rapid Transit (MRT) was the first rapid transit system in Asia to incorporate platform screen doors in its stations in 1987.[40] Additionally, the Singapore Mass Rapid Transit (MRT) is the first and only rail system in the world to incorporate platform screen doors consistently at all stations on the network with half height "psds" on the overground stations. Full height PSDs mainly manufactured by Westinghouse are installed at all existing underground MRT and sub-surface stations in Singapore, as well as at Ten Mile Junction LRT Station since its opening in 1999, but which has since been permanently closed. Future underground MRT stations will also have full-height doors installed upon opening. Half-height platform screen doors mostly manufactured by ST Electronics have been retrofitted into all elevated stations by March 2012 (starting with three elevated MRT stations in 2009), as well as all future above-ground MRT stations. The LRT stations at Sengkang, Bukit Panjang and Punggol also have half height platform screen panels installed beginning in 2015. These panels lack physical doors and vary in size according to their location on the platform. All remaining LRT stations received these panels by 2018.

There are two series of the full-height platform screen doors in use. The first series, made by Westinghouse, was installed at all underground stations along the North South Line and the East West Line from 1987 to the completion of the initial system in 1990. The second series of PSDs sport a sleeker design, producing less sound when the doors were opened and closed while incorporating more glass. The first station with these doors was Changi Airport MRT station which opened in 2002. All stations in the fully underground North East Line and Circle Line, which opened in 2003 and 2010 respectively, sport these new doors, also made by Westinghouse, although there are slight differences in their designs. The same doors used in the Circle Line also equip the rebuilt North South Line platforms at Bishan MRT station in 2009 following renovations in conjunction with the Circle Line interchange at the station. The Downtown Line features Westinghouse doors of a still-newer design, which is also found in Marina South Pier MRT station which opened in 2014. The Thomson-East Coast Line uses full-height doors by a different manufacturer, GE Transportation, in its stations.

Considered a novelty at the time of its installation, platform screen doors were introduced primarily to minimise hefty air-conditioning costs, especially since elevated stations are not air-conditioned and are much more economical to run in comparison. Since then the safety aspects of these doors have become more important, as highlighted by a series of high-profile incidents where individuals were injured or killed by oncoming trains since the year 2002—all occurring on elevated stations with no screen doors. The Land Transport Authority reports that there have been more than 220 cases of commuters trespassing on the tracks between 1991 and 15 September 2004, of which 87 percent were deliberate acts of trespass. Nine fatalities were recorded during this period, of which only one was an accident. Since September 2004 there have been six fatalities occurring on elevated MRT and LRT stations.

• 
  The first generation of platform screen doors, introduced with the Singapore MRT system in 1987. Seen here at Somerset Station, on the North South Line.
• 
  Second-generation platform doors at Woodleigh Station.These doors were introduced on the North East Line (which this station is on) in 2003. These doors have more glass than the first-generation doors pictured above.
• 
  Newest generation platform screen doors, seen here at Chinatown Station on the Downtown Line. This station was opened in 2013.
• 
  Half-height platform doors were installed at Yio Chu Kang station in 2011, 24 years after the station opened

Full-height platform screen doors on Seoul Subway

Yongdu Station of Seoul Subway Line 2 was the first station on the Seoul Subway to feature platform screen doors; the station opened in October 2005. By the end of 2009, many of the 289 stations operated by Seoul Metro had platform doors by Hyundai Elevator.[41] Seoul Metro Line 1, 2, 3, 4, 5, 6, 7, 8 and 9 were equipped with platform screen doors However, not all stations operated by Korail have completed installation. All stations in South Korea will have platform screen doors by 2018.[42] As of 2017, 100% of subway stations are equipped with platform screen doors in Daejeon, Gwangju, Busan, Incheon and Daegu.[43] The platform screen doors installed in Munyang Station in Daegu Metro have a unique rope-based platform screen named Rope type Platform Safe Door (RPSD).[44] A set of ropes cordoned off the platform from the rails. When the train arrived, the rope screen ascended to allow entry. This RPSD was also used in Nokdong Station on Gwangju Subway, but was removed in 2012, and a new full-height platform screen door was installed in 2016 instead.

Half platform screens were installed first in Provença FGC station (Barcelona) around 2003. Later doors were tested on Barcelona Metro line 11 before fitting them on all stations for the new lines 9 and 10, which operate driverless. In the Seville Metro this system is the one used since it was opened in April 2009.

Stockholm commuter rail has platform doors on two underground stations opened in July 2017, as part of the Stockholm City Line.[45] The Stockholm metro will receive platform doors in two stations during 2017 - 2018.[46][47] The underground Liseberg station in Gothenburg has platform doors which were built before its opening 1993. The reason was safety against the freight trains that go in this tunnel. These doors are built one meter from the platform edge and do not restrict the train type.

Zurich International Airport's Skymetro shuttle between the main building (hosting terminals A and B) and the detached terminal E has glass screen doors separating the tracks from the passenger hall platforms at both ends.

Lausanne Metro's Line M2 has glass screen doors at every station.

Taipei Main Station of the Taipei Metro is fitted with automatic platform gates

Platform screen doors were first installed on the Wenhu line (then known as Muzha line) in 1996. These days, all platforms on the Wenhu line are equipped with them. Initially, MRT stations were constructed without platform screen doors but were retrofit to include them over the years with the project completing in 2018. Since then, all new platforms are constructed with platform screen doors.

Sala Daeng sky train station, Silom, Bangkok

Platform Screen Doors were first installed on the Bangkok MRT System since it first operates. Followed by the Airport Rail Link System in Makkasan Station (Express Platform) and Suvarnabhumi Station (both City and Express Line Platform. BTS Skytrain system first installed the Platform screen doors at Siam Station. Followed by all the busy stations during rush hours. Today, Almost all stations on the Bangkok Electrified Rail System have installed the Platform Screen Doors preventing people from falling onto the tracks. BTS Skytrain system has installed PSDs on 18 stations out of its 44 stations. Both Purple and Blue Line of Bangkok MRT system has installed PSDs on all of its stations. Airport Rail link has installed a stainless steel fence to prevent from falling but has not installed an automated door due to a speed of the train is too fast that it will break the glass. All new stations in Bangkok must installed Platform screen doors as a rule.

Line M5 of the Istanbul Metro is equipped with automatic platform gates at every station.

Platform screen doors are installed on all the platforms in the fully automated Dubai Metro, as well as on the Dubai Tram (the world's first tram system to feature platform screen doors).

Platform screen doors at Westminster

The Jubilee line extension project saw platform edge doors installed on its new stations that were underground, and were produced by Westinghouse.[48] There are plans to install PEDs (which, similar to the Jubilee Line, will not reach to the ceiling) in existing London Underground stations along the Bakerloo, Central, Piccadilly, and Waterloo & City lines as part of New Tube for London.[49]

PEDs are present on the Gatwick Airport shuttle system, Heathrow Airport Terminal 5 airside people mover shuttle, Birmingham Airport AirRail Link and Stansted Airport Transit System. In these cases the purpose is safety, as there is a considerable drop on the other side of the doors.

Crossrail will have PSDs at all of its newly built underground stations,[50] except the stations at Heathrow Airport. The Heathrow stations will also be served by Heathrow Express trains, which have a different door layout.

The Glasgow Subway will have half-height screen doors by 2020.[51]

Full-height platform screen doors at AeroTrain Terminal at Washington Dulles International Airport

Platform screen doors are generally rare in the United States, and are almost exclusively found on small-scale systems. The privately operated Las Vegas Monorail system is currently the only general-purpose rapid transit system in the US to use platform screen doors. Honolulu Rail Transit will become the first large-scale publicly run metro system in the United States to feature platform screen doors when it opens in late 2020.[52]

New York City's Metropolitan Transportation Authority has not committed to installing platform screen doors in its subway system, though it had been considering such an idea since the 1980s.[53] Possible locations for platform doors include several stations along the Second Avenue Subway, but their installation presents substantial technical challenges, as there are different placements of doors on New York City Subway rolling stock.[54][55] The MTA is also interested in retrofitting platform screen doors on the Canarsie Line, along the L train, and on the IRT Flushing Line, along the 7 and <7>​ trains. However, it is unlikely that the entire New York City Subway system will get retrofitted with platform screen doors or automatic platform gates[56] due to, again, the varying placements of doors on rolling stock.[57] Following a series of incidents during one week in November 2016, in which 3 people were injured or killed after being pushed into tracks, the MTA started to consider installing platform edge doors for the 42nd Street Shuttle.[58] In October 2017, the MTA formally announced that platform screen doors would be installed at the Third Avenue station on the L train as part of a pilot program,[59][60] but the pilot was later postponed after funding for the doors was reallocated to an elevator installation project.[61]

People movers, systems that ferry passengers across large distances they would otherwise walk, make use of platform screen doors. These systems are common at airports such as Hartsfield–Jackson Atlanta International Airport and Denver International Airport. The Port Authority of New York and New Jersey uses full height platform screen doors at two of its systems: AirTrain JFK and AirTrain Newark (serving John F. Kennedy International Airport and Newark Liberty International Airport respectively). San Francisco International Airport has AirTrain, a 6-mile-long line whose stations are fully enclosed with platform screen doors, allowing access to the fully automated people mover. Chicago O'Hare International Airport has a people mover system which operates 24 hours a day and is a 2.5 mile long (4 km) line that operates between the four terminals at the airport and parking areas; each station is fully enclosed with platform screen doors allowing access to the fully automated people mover trains. AeroTrain is a 3.78-mile (6.08 km) people mover system at Washington Dulles International Airport in Dulles, Virginia with fully enclosed tracks including platform screen doors. The United States Capitol subway system, a train cart people mover system, uses platform gates.