PLATFORM DESIGN

Platforms, at their core, serve as designated areas for passengers to board and disembark from trains. This seemingly simple function holds immense significance for urban mobility. Globally, stringent design standards, life safety codes, operators operational methodology, and a range of transport planning principles ensure passenger safety and efficient operations.

However, despite train operation long history, dating back nearly 200 years, metro platform design has only evolved significantly in recent times. This complexity stems from the need to meet ever-increasing ridership demands, maintain uninterrupted service, fulfil public expectations for transport on demand, and more and more it is clearly the only sustainable transportation solution in the face of climate change.

Fig. Graphical illustration of Island, Side & Stacked Platform

The platform could be looked at, as a collective of the train & the tracks, the waiting area for the passengers ,and the area for the Vertical Transport (VT, lift, stairs and escalators) plus the VT themselves. These three in concert with each other then define the overall size of the platform and its particularly requirement & play a huge part in the overall size of the station box.

Empirical observation states that the two side platform configuration shown above - requires more VT, station are generally larger (Wider), MEP systems more expensive to design/construct/operate (Two sets of MEP services to run down from the level above), station are not best for passengers wayfinding, etc. However more often than not, the Trackside / Rolling Stock Engineering basis completely superseded the passenger requirements, sound Opex cost reduction, etc. More ranting, illustration in concourse section.

'The Platform', has to be sized to suit, Platform sizing or platform dimensions required have been discussed in more details under Station Sizing.

Platform sizing also pertain to the study of the actual numbers of VT elements such as Lift, Escalators and Stair that is required. This has been discussed in more details under the Escalator Section.

PLATFORM DIMENSIONS

Fig. Diagrammatic Platform Configuration

The size of the platform is defined by many criteria. Some of which are outlined below.

Platform Length

It would make sense that a platform is as long as the length of trains, either based on present, or future projected patronage basis. In certain systems, like the UK Network rail, their standards notes platform to be 5m longer, to address variances in train stopping. Which can be ignored if platform doors or gates are in place.

Nevertheless, for cities with small population, that has potential to grow substantially, or where ridership could switch modal system to a metro system, it may be worth designing a platform where the number of cars could be increased in the future – when such needs arises.

Platform Width

So, what should define the width of the platform? The Level of Service (discuss below) is one important basis. There are many other criteria's that govern this, some are debited below for reference:

Platform Screen Door / Platform Gates: When installed, this will enhance platform safety (Stop passenger, etc. falling onto the tracks), where by design standards could be relaxed, allowing passengers to be closer to the platform edge, thereby reducing the platform width.
Skin Effect: Additional free dimension required by certain metro systems, which potentially require platform to be wider.
Train on Fire Evacuation Scenario: may require station platform to be far wider than the Level of Service basis.
Modular or typical station typology: Whilst desirable, may require platform to wider than required for the projected patronage. More information to the right
Station Ends Plants: Width of such plants may drive the station platform to be wider. Generally, this should not be the case, however this may be the case sometimes, a considerable design review should be carried out to insure that this is not the case, as incremental increase in dimension of the platform has an exponential impact on the volume of the station, in turn cost of the project. Particularly in underground station typologies.
Special Event Station: Certain stations, say at remote stadium location, may have unusually large patronage during events, in which case the platform may be sized larger than normal patronage.
Etc.

Minimum Platform Width:

Many system will define a minimum platform width. Defined as a system wide standard, after which in early stages of design, the designer needs to calculated the width based on line wide design standards and given station patronage data's, both empirically via calculations, and also via simulations using software such as Legion, etc. This will then be considered to be the system requirements & basis of design.

Some Prescriptive Standards:

UK Transport for London (TFL) applies a min of 3m for side platforms, 6m between platform nosing. Caveats applies, design standards (Skin effect, etc.) needs to be reviewed for those req.

HK MTR requires a minimum of 3m for its platform width for their design standards. Impediments such as columns, short walls, etc. are allowed to impinge within this 3m zone . These dimension needs to be sized to actual patronage numbers.

Uniform Platform Width: Many system’s platform design, which are either end loaded, or have, say two VT connections along its length, may need a design criteria, where the platform width at these points are either wider (Dumb bell shaped), to address the anomalies of the passenger loadings, or other station planning basis is undertaken, so that a wider uniform platform width is not designed.

UK TFL provides a design criteria where 35% of the platform load occupies 25% of the platform busiest section, etc. So, platform could be sized accordingly.

Other system, such as HK MTR, or Bangkok MRT, have a platform typology, which generally defaults to around 4 banks of VT from the concourse level. This VT bank disposition usually uniformly spreads out the passengers and as such platform widening MAY not be required? Of course, this may be challenged if the computer simulation dictates otherwise; in which case the platform design need to be adapted to suit – not necessary via widening of the entire platform.

An important caveat here is to ensure that platform design, the location & number of VT elements is suitable enough to ensure that the platform is cleared of passenger from the last headway, before the next train arrives. This is discussed in other sections.

PLATFORM ELEMENTS

So, lets look at the other platform elements which one finds at the platform:

Platform Screen Door (PSD).

I remembered visiting metro stations in Moscow and St. Petersburg, where some station platform were hard to locate as the tracks side was hidden behind a continuous walls, punctuated by uniform opening with solid doors which corresponded to the train door, they opened when train pulled into the station, etc. It is impossible to know that is the trackside, particularly when this happens in a side platform config. or there are no passengers around. This design is indeed remarkable as this was built in the 60's & enabling such access control system or the needs for this is then is surprising. However the first modern PSD were introduced in Singapore MRT (Westinghouse Platform Screen Doors ).

The PSD has many functions, some of which can be as follows:

Ensure transit safety by stopping people, object, etc. from falling to the track
Mitigate operational delay by ensuring trackside integrity
Reduce station ECS (Cooling/heating) requirement, without PSD in place, the push pull effect of the rolling stocks will suck out the conditioned air from the station, into the tracks.
- - At the same time, the push pull effect of the train and the tunnel - provides free cooling + ventilation of the trackside is more effective when the PSD is installed, as the the piston force may be dissipated by the large platform volume
Enable some level of fire separation between the trackside and the station platform compartment
Reduce noise pollution into the station box from the trackside, etc.

It could be stated that the overall capital cost of these gates have operational cost saving after many years of operation, justifying the Capex/Opex measurement only.

2. Automatic Platform Gate (APG).

So why would you need a APG, why not use a PSD? Here are some key considerations why?

For stations that is naturally ventilated (At grade, elevated station), where prevailing air ventilation/movement is important, in these cases using an APG is important as it encourages wind movement more than PSD.
For the above station case, it means that platform/train on fire smoke ventilation is helped by this lower APG
The picture on the right MAY also shed the rains off the trains to the platform. Which nedds to be designed out

PLATFORM VERTICAL TRANSPORT DISPOSITION

This is an important element of station platform design. In traditional, older metro stations in London or Paris, as platform are designed around running tunnel/platform due to engineering and ground conditions. VT banks are connect off the platform tunnell, which take the passengers to entrances at ground level, as shown to the right.

As tunneling is a dark art and engineers do not want to take any risk. Or ground conditions, use of TBM construction,etc. may end up with such dumbbell configuration. Setting the standards for station planning principles in many countries.

If the station box is not very deep, many other systems would opt for a VT configuration that is diagrammatically similar to the one on the right.

Possible for both island or side platform configurations.

So here are comments on this configuration:

Spatially the Architecture could be stunning
Wayfinding and decision points are set at platform level
Limited flexibility for ToD adaptation
Fire Engineering and smoke management design critical, large volume either purged or extracted via required air change, etc. Single large compartment
Passenger movement at the platform level may not be highly desirable, as two banks of VT will not only need to cater to larger no of train car, but that they will need to double back, etc.

Fig. Station Longitudinal Sectional. Such planning are common to Singapore metro, etc.

Whilst the upper configuration may be suitable for medium to large systems, the section to the right could be applicable for medium to small systems (LRT), where the 2-4 car is all that is required, patronage speaking.

Here the second bank of VT MAY not be required.
One Up/Dn escalator can easily operate the operational needs (1 Escal=~7000 Px/Hour)
20-25 m long train car (Say 8X-100m long platform) requires careful evacuation VT element placement. for sure additional evacuation Stairs.
A single VT bank MAY also limit number of entrances, or starts to limit the overall catchment of the station
Other MEP issues are similar to the basis discussed above

Fig. Station Longitudional Section. Such planning could be suitable for smaller cities where population is limited. Such as Copenhagen, Macau, etc.

The configuration to the right could be termed the Hong Kong model, which has found its way around many parts of the world, such as China, Malaysia, Thailand. etc.

As number of cars are large, the number of VT could be in 4 banks, or as required by the patronage
The disposition of the VT also shows an equal distribution of the passengers at the platform level.
All VT leads to the upper level. Meaning that there is no decision point to be made at the platform level.
Such system will/should have different Fire Engineering basis; in the case of HK MTR the platform and the concourse is located in two compartment, where the VT takes you to the above concourse compartment, which then enables the ToD & commercial successes of the MTR

Fig. Station Longitudinal Section common to Hong Kong MTR. Arguably other cities and systems have not taken the advantage of the ToD planning that HK has managed to leverage wih this system.

More VT (Escalators) also means that egressing passengers from short train headway can be cleared off before the next trains arrives.
There are other advantages of the VT disposition, which needs to be read in conjunction with the other chapters

OTHER CONSIDERATIONS

Fire and life safety (FLS) are paramount considerations in station design. This section delves deeper into these critical aspects.

However, FLS requirements often appear overly stringent and standards vary significantly across countries. This raises questions: Why are the requirements so demanding? Do these requirements truly reflect the evolution of railways from highly combustible systems to a more engineered approach to life safety?

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