The MTR in Hong Kong is one of the heaviest used and most efficient rapid transit railway networks in the world: I have previously blogged about the signalling systems and platform operations used to achieve the short headways between trains, but what happens to trains at the end of the line?
On most railways the terminus is the bottleneck, as trains need to change direction and tracks before they can depart on another journey. The MTR is no different, running an intense service with average train frequencies being as short as 2 minutes. The most common terminus layout on the MTR network is an island platform with a scissors crossover linking the two tracks at the approach side – 12 out of 20 termini stations are laid out this way:
- Yau Ma Tei on the Kwun Tong Line.
- LOHAS Park on the Tseung Kwan O Line.
- Chai Wan on the Island Line
- Hong Kong and Tung Chung on the Tung Chung Line.
- Asia World Expo on the Airport Express Line.
- Hung Hom on the East Rail and West Rail Lines.
- Lok Ma Chau and Lu Wu on the East Rail Line.
- Tuen Mun on the West Rail Line.
- Wu Kai Sha on the Ma On Shan Line.
Second most common – island platform with a scissors crossover at the far side, with two dead-end stub sidings beyond.
- Tiu Keng Leng on the Kwun Tong Line.
- North Point on the Tseung Kwan O Line.
- Wu Kai Sha on the Ma On Shan Line.
There are also a number of oddball stations with their own unique track layouts.
- Po Lam on the Tseung Kwan O Line has a single platform, the two running lines merging into one just before the platform. The station is on a little used branch line, so the minimal infrastructure makes sense here.
- Hong Kong Station on the Airport Express Line only uses one of two platforms, with a crossover at the approach/departure end linking the two running lines. Again, this line operates on a 12 minute headway, so there isn’t any capacity constraints here.
- Tsuen Wan has a pair of side platforms, with trains collecting a new driver at the down platform, before reversing in a turn back siding beyond the station, and arriving into the up platform. The odd layout dates to the since abandoned plans to build a station a bit further along the line, and the need to provide access to the adjacent train depot.
- Sheung Wan on the Island Line also has a pair of side platforms, but only has a single turn back siding in the tunnel beyond the platform. Given the 2 minute headways on the line in peak times this layout makes little sense, but presumably with the use of a second train driver a train can be turned around quickly enough.
- Central Station on the Tsuen Wan Line has an island platform linked by a scissors crossover at the near end, but it also has a turn back siding at the far end.
Despite island platforms and single crossovers being in common use on much quieter railways, the MTR manages to push the track layout to the limit, with a number of optimisations being made to minimise the time trains spend blocking other trains.
The first is “drop-on drivers”, which is when a second train driver will be waiting on the platform, ready to take the arriving train back out again.
This technique is used at most termini during peak times, the process is as follows:
- Driver leaves the cab of train 1,
- They can have a short break,
- Walk to the departure end of the platform,
- Wait for the next train (train 2) to come in,
- Enter the cab of train 2, and depart once the signal changes.
The driver of train 2 then repeats the cycle.
The second optimisation on the MTR is increasing the speed that a train arrives into the platform, which reduces the amount of time each train spends blocking the biggest bottleneck of the railway station – the scissors crossover at the arrival end. Unfortunately this idea falls over if the tracks end immediately after a station and the train doesn’t stop as intended, so this leads to the third optimisation – overrun tracks at the departure end, so that a train still has somewhere to go until it is stopped by the emergency brakes.
Virtually every station is provided with overrun tracks, with some being simple like this set at Disneyland Resort Station, with the fixed signal at the end of the platform indicating where to stop during normal operations, with the set of buffers located before the end of the line to stop any runways before they eat concrete.
The length of the overrun tracks at terminal stations affects the level of service that can be provided on the line – longer tracks means higher speeds, quicker turnarounds, more trains in motion, and more passengers carried.
One extreme example is Hong Kong Station on the Tung Chung line, where current short overrun tunnel limits the overall capacity of the railway. The station was built in the mid 1990s on a piece of reclaimed land which only permitted a short overrun, with further land reclamation currently underway to allow a longer overrun to be built – the MTR justifies the work here:
- Why we need to extend the Airport Railway Overrun Tunnel
- For safety reasons, an overrun tunnel of sufficient length is required at all terminal stations to ensure trains failing to stop at the design position, as a result of human error or defective equipment, would not collide with the tunnel end.
- The existing 84-metre overrun tunnel for the Airport Railway is acceptable for the current service level.
- But, to enhance capacity, the existing overrun tunnel has to be extended by 40 metres as a matter of urgency.
- The MTRCL forecasts that the current overrun tunnel will only remain acceptable until 2006.
- Why we need the Extended Portion of the Airport Railway Overrun Tunnel
- MTRCL needs a further extended portion of 460 metres to allow the Airport Railway and Tung Chung Line to operate at full design capacity.
- Both railways are forecast to reach full design capacity by 2014, but provision for the project must be made in Central Reclamation Phase III.
Many of Hong Kong’s stations are in tunnel, but others are up on viaducts. Chai Wan is the terminus station on the Island Line where trains run every two minutes, and a very impressive looking set of buffers is provided to catch fast moving runway trains before the track runs out.
In this view you can see why the stakes at Chai Wan are so high: a runway train would run off the bridge and into the second floor of a shopping centre!
Tuen Mun on the West Rail Line is another station up on a viaduct, but the set of buffers there are on the small side – trains here run only every 3 minutes, so speeds are a bit lower.
None the less, the five story drop from the end of the line into the river below ought to serve as an incentive to pull up in time. I hate to see what would happen if the MTR bought trains from the same place Melbourne did…
- Complete MTR track diagram at the ‘MTR之今昔’ enthusiast website.
An important feature of some of the reverse in platforms termini in Hong Kong is that the driver starts the door closing sequence before the train has a green signal. This saves vital seconds in dispatching a train, and makes for more efficient use of the crossover.
At reverse in sidings termini, trains are not checked too see if they are empty. Thus arrival platform dwell times are approx. 25 secs compared to more than 60 secs on London Underground. This allows for higher frequency in Hong Kong.
Pingback: MTR train cliffhanger? - Checkerboard Hill
Pingback: Extending the MTR using a tunnel *dismantling* machine - Checkerboard Hill