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STATION OPERATIONAL AND EVACUATION SIZING
STATION OPERATIONAL AND EVACUATION SIZING
Fig. Potential Station Element Sizing Matrix/Flow
Operation & Evacuation
Operation & Evacuation
Sizing discussion in this paper relates to sizing for operation, and sizing for evacuation. Two distinctly different requirement, both has to be designed for compliance.
All are for operation sizing, UNO
We will look at the station sizing chapter in many small steps, Let's start with the line capacity.
We will look at the station sizing chapter in many small steps, Let's start with the line capacity.
System Capacity!
System Capacity!
There is nothing magical, or highly scientific about system passenger capacity (Any mode, be it trains, bus, cars, cable car, etc), or how many passengers can a system carry, or lines can handle in a given period of time, over day, etc.
Simplistically it can be broken down into:
How many passengers a train car can carry?
How many cars your train has?
What is the minimum headway of your system?
What is the minimum dwell time of the train in the station?
Looking at the 4 keys above, you could summarise, comment as follows:
Maximise the handling capacity of each train car.
Make the train as wide as possible? This increases available width/capacity for passengers. (This statement is important design pivot in station design. In most other aspects, you may wish to make the station as narrow as possible (Physically), as any increase in width will add to the volume of the station and its exponential cost. However, for trains and their cars, this is an exception, as trackside dimension are reciprocal to the overall capacity of the train/system).
Link all the cars, allow passengers to move from cars to cars, even out the passenger car density
However, it is almost absolutely challenging to get the rolling stock design dimensions changed.
As less seating as possible, more people standing.
It also does not mean that you can pack the car like a sardine, in which case the passengers will not be able to get out, or the train dwell time will be too long, and the headway may suffer.
No. of cars is important. As this exponentially increases the capacity of the system. So having the option of more cars in the future, is also good.
The minimum headway of the system will depend on many systems, including:
The number of trains you have. Longer line, with more stations, means more trains set required
System signalling needs to be modern
Train dwell time in stations needs to be optimised, etc.
The minimum dwell time will depend on many factors:
Does the train have enough doors, or wide enough?
Does the platform design right for the capacity and passengers able to get in and off the train easily? etc.
A quick line capacity in one house could be:
> Car Capacity X # of Car X Number of trains in one hour, Say:
> 250 people X 8 car X (60 min / 2(Train every 2 min (headway))
>2000 people X 30
>60,000 passengers in one hour. Which is an absolute number and cannot be increased, unless some other system design measure are made, which is outside the remit of this paper.
The above will definitely be dissected by the traffic, system and other Engineers in many ways. The true numbers will be given to us, the system physical designers of the built form; however having a holistic understanding is a good base, an important base.
Station sizing for Evacuation
Station sizing for Evacuation
The above sizing information's, guides and methods are for operational requirements only. For the evacuation requirements, a quick overview will be provided below.
Fire Types
Fire Types
There will be many different emergencies, or fire types in and around the station. Some of which are as follows:
Train on fire
Platform on fire
Concourse on fire
Passages or entry on fire, etc.
Train on fire: In this scenario:
The train on fire will be a fully loaded train, which will stop at the station and the passengers will evacuate on the platform
The existing passengers on the platform, or platforms, etc (Within the station box) will also need to evacuate
For the platform, all the passengers need to evacuate within the mandated time (4 min as per NFPA130, 4.5min in HK MTR, etc)
Numbers of VT will need to be sufficient to evacuate the total passengers from the platform.
The VT capacity will be different for evacuation, plus the escalator availability will be based on the agreed code. Please check Fire Engineering section.
Various systems will have a nuanced requirements for the evacuation strategy, and the requirements. Refer station fire engineering strategy, NFPA 130 or local systems operators design standards, etc.
Platform Fire. In this scenario:
Most of the above applies. Plus,
Except, there will be no detraining. Only passengers who are on the platform, station box need to evacuate.
There will be substantially lower number of passengers. Which are stipulated in the owners' requirements and the station sizing documents.
The location of the fire is also important. If you have a fire in front of the main VT, then this may not be available, and passengers will need to use the other available VT's. So, such parameter and available size will need to be justified
Concourse Fire. In this scenario:
Similar to platform scenario. Plus,
Passengers on the platform may not need to evacuate, as they could leave on the next available train. However, this depends on the fire engineering strategy, operational strategy, etc.
Similar to the plat fire, one exit (Passage) may not be available due to fire in front of this passage, so suitable egress path and size will need to be designed for.
Passages or entry on fire, In this scenario:
Similar to Concourse fire. Plus,
All passengers will need to evacuate via the other available passages/entrance.
Station Sizing
Station Sizing
Every dimensions/size of our built form can be deterministically determined, while also meeting the minimum. statutory requirements. The same is almost the case for the requirements of our transit stations. Most of the requirements in the transit systems are determined by the design standards followed by the system operators, which may seem excessive, but have been rationalised in a deterministic manner.
There will be distinctly different requirements and basis of design for operational side, compared to designing for life safety or emergencies requirements. Which one could say, are the difference between designing for daily operations (Level of Service, comfort) and designing for emergencies (safety and evacuation).
Design standards from the system operator, local building & statutory codes, international standards such as IBC, NFPA, etc. can all be used for your basis of design - as long as these have been reasonably reviewed, agreed and accepted by the governing authorities.
Whilst many of these dimensions/requirements will be tabulated by both the Transport Engineer & the Fire Engineer, it is imperative that the station planner (Architect) take the leadership in these requirements and guide the expert in station sizing and fire engineers towards creating a thoughtful station size.
Neuferts Architects Data
Author:Ernst Neufert
Date published: 1936
Pedestrian Planning & Design
Author:John J Fruin
Date published: 1971
Two seminal books/author. The first informs many of our anthropometric many of for the built forms, whilst the second gives us the transport planning 'Level of Service 'basis, that makes up much of the transport sizing world
PRESCRIPTIVE SIZE FOR PLATFORMS
PRESCRIPTIVE SIZE FOR PLATFORMS
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 requirements. 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 area required by certain metro systems, which potentially may require platform to be deeper.
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.
LEVEL OF SERVICE CALCULATION FOR STATION SIZING
LEVEL OF SERVICE CALCULATION FOR STATION SIZING
Platform Sizing
As noted above, platform length may be a given, hence if platform needs to be sized, then the width may be the only give ! In which case the sizing is governed by the Level of Service.
Level of Service (LoS)
The Fruin LoS, illustrated above, could be used as a guide to size spatial dimensional requirements. Using the below LoS standard, The platform is sized to suite the patronage figures.
Different metro systems will require their stations spaces to be sized or verified to an agreed standards. Here are some requirements.
UK: Network Rail Network Rail Design Guidance references the Fruin standard and requires platform queuing areas to be designed to LoS C (typically 0.9 m² per person). Their standards further differentiate queuing and walking areas, providing a more nuanced approach.
Transport for London (TfL) also recommends LoS C (0.9 m² per person) for London Underground stations. Similarly a nuanced approach, with spaces allocated for 'skin effect', etc.
Hong Kong MTR: While their Design Standard also recommends LoS C, LoS D may be acceptable in specific situations.
Singapore LTA: Similar to Hong Kong, their standards recommend LoS C.
Fig. TFL's Station Capacity Planning Document
©TFL
Fig. Platform Sizing Tabulation
The above table is a very simple tabulation that does not take into consideration many of the nuanced criteria's that may be required in the design standards, such as skin effect, setback from VT's, etc
Diagrammatic view of LoS C below:
PASSAGE SIZING
PASSAGE SIZING
Passages, or 'Adits' as they are called in Hong Kong, are an important part of the station, as it connects the station box to the entrances. The capacity calculation and sizing criterias are also different for these spaces. here are comparison between the TFL and the Hong Kong MTR.
TFL Passageways Req Extracted:
3.6.1.10 When calculating capacity in routeways with square walls, 0.3m 'edge effects' shall be added to each wall, except where noted in 3.6.3.1 and 3.7.5.1.
Here the 'edge effects', skin effects, etc. all are offsets required to be provided from the walls, as human factors dictates that people are reluctant to walk very close to the walls. Hence passageways will be 0.6m wider than the LoS required.
The below criteria exempts the 'edge effects', if the side walls are circular in cross-section
3.6.3.1 Circular cross-section passageways shall satisfy the following requirements;
The width of the floor shall be no less than the calculated passageway width, but without adding the sidewall 'edge effects’.
The internal diameter of the passageway (i.e. with finishes applied) shall be no less than the calculated passageway width with the sidewall 'edge effects' included. This requirement and that above do not allow any local reductions to width, for example by advertising panels that 'square-off' a circular cross- section passageway.
Fig. Illustrates adit width and additional dimension required in some standards
Tables in this section ©TFL Ltd
The above is an example of calculating passageways requirement using patronage datas and static calculations. Whilst the below shows the LoS table; where an LoS D&C (One & two way respectively) are required. These do not take into consideration the 'edge effects', where 0.6m extra width needs to be added.
Hong Kong MTR Passageways Req Extracted:
The HK MTR Design standards requires adits sized for different scenario:
For emergency evacuation, the capacity is much higher
Whilst the design factor for normal operation is given, when station are newly designed, the capacity of the adits are uplifted to allow for more capacity in the future.
A skin or edge effect is not considered.
Two observations from the Hong Kong Standard for Passageway
You could question why the entrances and the adits DF or criteria's for new stations are uplifted? The standards calls for this due to additional capacity in the future, however another important factor is that the station in HK are a big ToD pivot point, where non-passengers use the underground adits & elevated footbridges connected to the station to move around the city. Hence these help to account for the non-rail passenger sizing also.
Why is skin or edge effect not considered in the design? One reason is that the HK is a very dense city with pavements where people are used to an LoS of D, etc. Hence one could stated that the public's expectation for additional space around one's elliptical boundary is not there and human factor needs for walking in close proximity to the wall is also not acute.
Comparison between the two standards
Comparison between the two standards
It is very tempting to rush to judgement about the above data comparisons. However the background of the two system is based on perhaps different philosophy, or basis of its operation. Nevertheless here are some views on the above numbers:
The numbers starts to even out when the people using the passageways are higher
The TFL standards are much more forgiving, whilst the HK MTR is much more robust. So what does that mean? Possibly that the former system can handle much more people than it has been designed for, whilst the latter may not have any additional capacity if the designed values are reached? Or there about!
Using Uplift Factors for Peak Passenger Demand in Station Design
Using Uplift Factors for Peak Passenger Demand in Station Design
When patronage data are given by the authorities, they may be a whole figure. Say projected population in the first day of the system opening, 15 years after that and an ultimate figure. Also, they may be data's that is given per year, or we could take a proportional number from given figure. These extrapolated, yearly data's is not suitable for use, say for instances:
Weekend may have less passengers (Or in certain stations more)
Weekdays will have more passengers in the morning (AM), when people are going to work, etc.
So, it becomes imperative for transport planner, on behalf of the station design team to make design assumptions based on the design standards. Most of these data's will be driven down to a peak or peak in peak one minute, which can then be used to size various elements of the stations, such as VT, areas capacity, etc. Here are some for reference.
London Underground:
London Underground:
TFL S1371, Station Capacity Planning
Uses patronage data's for the Peak minute. Which is taken from the peak 15 minutes, divided by 15. If this is not given then the demand data is uplifted by 120%
Further Table 2 of the same document also provided specific guidance where data are not available.
Singapore
Singapore
LTR Architectural Design Criteria, Section 2.2.1 defines this to be 130% of the peak hour patronage data, The nomenclature for this minute is 'peak within peak'
Hong Kong
Hong Kong
MTR Design Standard Manual Section 5.1.2.4 defines 'peak within peak' data to be 120% of hourly data
So, from the above it is clear, that any patronage uplift of 120-130% of the hourly data is a sound number to use.
THE ROLE OF THE ARCHITECT AS STATION PLANNER
THE ROLE OF THE ARCHITECT AS STATION PLANNER
Architects play a central role in station planning. A strong understanding of the core principles outlined in this chapter is crucial for architects leading station design projects.
In some countries, complex station projects may involve a team approach. Highly skilled professionals from various disciplines collaborate, iteratively integrating their expertise to achieve a holistic design solution. However, programme constraints might necessitate a more streamlined approach with the architect taking the lead.
Mega Event Station.
Mega Event Station.
Station sizing is generally planned for hourly and other 'peak in peak' patronages. It is possible that some station may have stadiums, concert halls, etc. nearby, which may load the station in an adverse manner, require a controlled management of passengers entering the stations. Else there will be a systemic failure in the transit system.
BS9992, makes recommendation that Stations regularly used for access to events, should be designed to cater for that loading. The key word is 'regular', Despite this, it may be possible that that the regular event may have substantial passenger numbers, in all cases a management protocol needs to be set in place, so that passengers entering the station is controlled well outside the station box, let in a controlled manner. It is important to highlight that uncontrolled passengers at the platform area will be detrimental to station safety and security.
Whist it is not possible to discuss the potential magnitude of passengers that could enter the station in this paper. If you take into consideration that an 8-car train, with around 3000 capacity and 2min headway, will have an overall line wide capacity of around 90,000 people per hour (Which is a large transit system by any global standard). A large stadium with even 1/4 that capacity could potentially cripple the smooth operation of any system, if these passenger numbers are not controlled, and drip fed into the system. Hence making a huge station with lots of stair, escalator, wide passages is almost useless, as the rolling stocks will not be able to handle the load.
Hence a management strategy is very important, in stations. Not only to handle these events, but to routinely make drills for all events that could take place, in and outside the station, and its impact to the station operation mitigated.
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