UNDERGROUND STATION

Stations are placed underground, not only to maximize the transport potential of the city, but also to visually mitigate the impact of elevated and at-grade structures, despite the initial higher capital, or operational cost of such systems.

Underground stations follow different sets of life safety codes, fire engineering principles, planning basis, approval channel, etc. This complexity is so significant that, that systems around different countries can look similar, but will differ in their approach to delivering their own basis of needs for life safety, security and operationally taking passenger to their destinations.

Considering that railways and stations have existed for almost a thousand years, the evolution in their design and regulatory requirements, particularly in the last 30 years is truly remarkable.

Cavern, TBM platform tunnel, etc:

In a nutshell, all underground station planning is mostly predicated on two key requirements; the geotechnical condition, and the civil/structural engineering requirements and how to construct this safely and efficiently.
The deeper a station goes or the more complex the ground conditions, the exponentially higher the costs become for building both the station and the tracks.

Underground Station Sub-Typology:

The station underground is broadly classified based on the engineering & construction requirements, which in turn has a ramification on station planning, and the extensive design expertise required.

Cut & Cover: Where the tracks and station box are cut into existing street, or ground, covered over after construction is completed. The first three sketches to the left illustrate this. Also shown over the station box is a nominal ground cover, left to allow the city to pass their utilities, etc over. Whilst in some engineering sense, simpler that other deeper sibling, the cut and cover box still need to be stabilised underground. Different geological conditions will require this box to be built with different structural/civil/geotechnical engineering basis - diaphragm walls station box (Constructed all the way to the rock stratum), RC box with piles, or RC box with minimal foundations if the ground condition stable / no UG water pressure/displacement exists.
TBM Platform Station (Last sketch to the left), may also be frequently used in difficult ground conditions and it obviously needs to be designed differently. Or:

Cavern station, if the ground condition allows you to drill and blast, etc.

All of which means that the station planning will need to respond to the engineering requirement at its core.

Underground Station Planning: A Holistic Approach

Effective underground station planning requires a holistic approach. Station planners must consider all elements - tracks, platforms, concourses, passages/adits, entrances, and more; as system thinking, all parts of a larger system. This integrated design approach fosters a consistent and recognizable architecture across the network, simplifying wayfinding for passengers and streamlining station management and operation.

A modular, system-wide design strategy achieves these benefits by creating reusable station components. However, there may be instances where a unique "master station" is warranted, with a design that prioritizes aesthetics or serves a specific purpose beyond the standard model.

If you drill down a bit. A station planner needs to understand the systems and the processes for all the MEP and systems that end up underpinning the station. These needs to be laid in the most efficient possible manner, to arrive at a station design that is fit for purpose.

Beyond these considerations, user experience, passenger comfort, and placemaking principles remain crucial aspects of station design, requiring further discussion.

Some sketches for the complex and wonderful systems in a station

Operational System Design & Complexity

Underground stations require the integration of numerous engineering systems for smooth operation. Beyond life safety systems, these include:

Power Supply: A reliable power distribution network ensures uninterrupted operation of all station systems. Power system is also backup for emergencies.
Environmental Control System (ECS): MVAC systems maintain a comfortable and safe environment for passengers.
Telecommunication Systems: These include systems for rolling stock control, station management, passenger information displays, and public announcements, mobile signals, etc.

Fig. General spatial division in East Asian Stations

Additionally, stations require dedicated spaces for:

Operational & Staff Facilities: Control centers, maintenance rooms, and staff break rooms are essential for efficient station management.
Emergency Services: Dedicated spaces ensure fast response from police and first responders.

Some metro systems, like those in Singapore and Moscow, are even designed to serve as shelters during emergencies. All these functional elements contribute to the significant underground space required for a station.

Interestingly, only about 25% of this space is typically dedicated to public areas for passengers.

This highlights the challenge and importance of optimizing station design to maximize usable public space while accommodating the complex network of systems needed for a functional and safe underground environment.

Life Safety Design Basis for Underground Transit Systems:

A holistic approach to fire safety and life safety is essential for underground transit systems. This goes beyond prescriptive codes (NFPA 130, etc.) and incorporates fire engineering principles to develop a comprehensive strategy for all sections (tunnels, tracksides, stations, etc.). Each area will require specific design considerations for fire suppression, smoke management, and evacuation. A well-designed system ensures not only safe access for first responders but also efficient evacuation routes for passengers and personnel trapped during emergencies.

Station planners must understand not only trackside fire safety but also the overall fire engineering strategy/systems for the station and entire line. Close collaboration with fire engineers, MEP engineers, etc. is crucial to achieving an optimal station layout that prioritizes not only passenger & people safety, but also ensures that the transit system will be up and running in the shortest time after an incident.

Underground station will have substantial plantroom requirements, with associated ducts, shaft and compartmentation needs, which the station planners need to champion its location and adjacencies, working closely with the MEP team. These are spaces that is dying for AI to come and help with.

Please refer to that FLS section for more information's.

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