Platform gap
A platform gap is the space between a train car and the edge of the station platform, often created by geometric constraints, historic legacies, or use of partially compatible equipment.
Many high-quality bus rapid transit systems also use high platforms at station stops to allow fast and efficient level boarding and alighting, but potentially leaving hazardous gaps between the platforms and the buses. Alignment setups such as Kassel curbs help to reduce platform gaps without requiring time-consuming manual alignment at each BRT station stop.
Definition and measurement
A platform gap has two component measurements:- vertical
- horizontal
Straight platforms
Curved platforms
In real-world situations, stations are often constrained by limited space, legacy designs, and track geometry or roadway layout. Stations may have to use a compromise design, with a platform curved in a way that will allow a vehicle or train to arrive and depart without mechanical interference, but which leaves unavoidable horizontal and possibly vertical gaps between the cars and the platform edge. These spaces are caused by the geometric gap between a curve and the straight-line chord or tangent formed by a railcar or bus in proximity to a platform. These types of gaps are geometrically intrinsic, and cannot be eliminated as long as the platform is located on a curved or banked segment of track or guideway.When passenger car doors are located only at the ends of each car, platform access from a concave platform is preferred, since this brings the car ends in closest proximity to the platform edge. By contrast, a convex platform would leave the largest possible gaps between the car ends and the platform edge, making this design undesirable and thus rarely implemented.
An example of platforms designed for access from the concave side is at Lansdowne station in Boston, where side platforms for both the inbound and outbound directions are located to reduce platform gaps to commuter rail trains of the Framingham/Worcester Line. Concave and convex gaps also exist in several MTR stations in Hong Kong, particularly on the East Rail line, which was built on the historic Kowloon–Canton Railway line.
Gap fillers
Mechanical platform edge extensions known as platform gap fillers may be used to bridge the gap between platform and vehicle. These stopgaps require careful alignment of the vehicle upon arrival, and careful synchronization to avoid serious damage caused by departure of the vehicle before the extenders are fully retracted. They increase station dwell time, and introduce safety and maintenance concerns of their own.Alternatively, the gap fillers may be mounted on the train, and linked to the door operating mechanism. They may be found on modern trainsets, like various versions of the Stadler GTW and the British Rail Class 555 for the Tyne and Wear Metro. Train-mounted gap fillers eliminate the need for careful alignment and, as the driver only gets the signal that the doors have closed when the fillers have fully retracted, require no special synchronization on departure. Moving all active components of the system to the train instead of the platform allows maintenance to be performed in a shop, rather than in the field.
Germany
Many regional trains in Germany come with platform gap fillers, such as the Bombardier Talent 2. On subway networks, they have also become more common, as evidenced by the Nuremberg U-Bahn whose 1970s first generation VAG Class DT1 do not have them but whose VAG Class DT3 of the 2000s and 2010s and VAG Class G1 of the 2020s come equipped with automatic gap fillers.On the Berlin U-Bahn, which has two different loading gauges, so-called Blumenbretter bridging the platform gap were attached to Kleinprofil trains that ran on Großprofil lines at various times of rolling stock shortage.
Hong Kong
Platform gap fillers were tried on the platforms of Lo Wu station on the East Rail line in 2009 due to the difficulty of installing platform screen doors on the [|curved nature of the platforms]. They were planned to be installed at other stations along the line along with signal upgrades. However, during the trial period, MTR found that the time taken for the gap filler to fully extend took 15-20 seconds and so greatly increased dwell times of trains. It was decided unsuitable for service. After the trial period ended in October 2009, the platform gap fillers were not used until it was finally removed during a platform-strengthening maintenance operation. Plans to install it on other stations of the East Rail line were also abandoned.Japan
Some Japanese railway stations have platform gap fillers, which are known as movable steps. Over 200 fillers are used in the Tokyo subway. In addition, there is a program to retrofit platform doors for increased safety on Tokyo subway lines.Singapore
has committed to specifying its newer trains with gap fillers, to reduce the incidence of platform gap accidents in its crowded stations. Platform gap fillers are used in the Mass Rapid Transit system of Singapore, namely the North South MRT line and the East West MRT line. Platform gap fillers are also planned for installation on trains on the North East MRT line and the Circle MRT line as well, because newer trains can be equipped with gap fillers.Thailand
The Airport Rail Link has installed platform gap fillers at all 8 stations on 12 July 2019 to enhance passenger safety and convenience. These gap fillers bridge the space between the train doors and platforms, providing a safer experience for passengers. The system connects the airport to the city center, with the platform gap fillers made from locally sourced natural rubber, supporting domestic production and ensuring high quality.United Kingdom
With the introduction of the New Tube for London, Transport for London are hoping to introduce platform gap fillers on the Bakerloo, Central & Piccadilly lines at curved platforms such as Bank, where the gap between the train and the platform can exceed.United States
New York City Subway
The Interborough Rapid Transit Company's first cars were built with only two doors on each side, at the extreme ends of the car, lining up with the curved platforms so as not to leave a wide gap between the train and the platform. When the IRT modified existing cars and ordered new cars with a middle door, gap fillers were needed because the middle door was not near the platform. After the City of New York bought the IRT in 1940, new car designs had the end doors away from the extreme ends of the car body, which also required the use of gap fillers at certain stations.Stations equipped
IRT stations with gap fillers are:- South Ferry, outer loop. The station closed on March 16, 2009 and was replaced by a new station which does not require gap fillers. After the newer station was damaged by flooding during Hurricane Sandy, the original loop station was reactivated as a temporary terminus on April 4, 2013. The repaired newer station reopened on June 27, 2017.
- Brooklyn Bridge – City Hall originally had gap fillers on the express platforms. These were deactivated when the station was extended northward. These gap fillers are still in place and can be seen just south of the current platforms.
- 14th Street – Union Square has gap fillers on both tracks on the downtown platform. There may have been gap fillers on the uptown express platform. A new design of gap filler was installed in 2004 to provide maintenance access from the platform rather than requiring crews to stand at track level.
- Times Square had gap fillers on Shuttle tracks 1 and 3. They were mounted under the platform rather than on it, so they were not ADA accessible. They were removed in 2021 when the station was rebuilt.
Utah Transit Authority
Equipment compatibility
In some rail systems, significant platform gaps may also occur because of equipment and platforms designed to different and somewhat incompatible height and width standards. This situation may occur especially when previously separate rail systems are consolidated, or start to interoperate, thus allowing equipment to be moved onto tracks where it had not been used before.In 2007, public testimony by the acting president of the Long Island Rail Road cited the need to interoperate with freight service and other passenger services such as New Jersey Transit and Amtrak, in addition to its own diverse rolling stock, as complicating and slowing efforts to deal with platform gap hazards.
Other contributing factors
Other variables that can increase platform gaps include rail wear, wheel wear, condition of the railcar suspension, and passenger load. A further complication is super-elevation, deliberate tilting of the railbed to allow faster travel around curves. This factor is especially relevant on systems where some express trains operate non-stop through local stations located on curves. Higher pass-through speeds also increase railcar sway, requiring even larger physical clearances to avoid platform strikes.Specifications and limits
In the US, the Americans with Disabilities Act requires that platforms be “readily accessible to and usable by individuals with disabilities, including individuals who use wheelchairs ”. However, this rule only applies to new construction or major renovations of stations. A 2009 report to the New Jersey Department of Transportation observes that ADA rules specify that "At stations with high level platforms, there may be a gap of no more than 3” horizontal and 5/8" vertical between platform edge and entrance to the rail car. However, currently no passenger rail system in the U.S. has been able to achieve this without the use of manually operated 'bridge plates'.”, the US Federal Railway Administration recommended platform gap maximum limits of, and on curves.