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At grade station typology arises from the track being on the ground, the platform is either in the center, or on the sides. In such typology, passengers need to either go under or over the platform, to the ticketing hall/concourse and then get to the platform. Of course for many LRT/BRT systems with limited headway and manned trains, the tracks crossing could be done at grade, before & after the platforms
The obvious cost advantage of such system is limited by the land sterilisation due to the tracks and its urban design restrictions.
For such station types, passengers will navigate mostly via the concourse level, which could be either above or below. Station wayfinding is much more easier and line of sight to civic infrastructure, daylighting, etc. will help people movement considerably. There are limited reasons why at grade station should be side platform. We see later in the concourse section, where you will begin to appreciate the constraints of side platform on the concourse level - particularly if this is on top.
For both the platform section above, a more naturally ventilated platform section is desirable, as air conditioned platform MAY need smoke extraction, etc. Hence for a naturally ventilated platform, an APG is desirable, as its low height will help cross wind circulation.
There are fairly good chances for this station box to be designed with a greater architectural expression, human centric and potentially in a very carbon neutral manner.
Here the discussion on carbon neutrality needs to be discussed earnestly, engineering and client team needs to be more demanding. Whilst carbon neutrality is only from an operational point of view, advances in solar cell technology and increase energy output (~50%) will allow more of the fitments to be powered from these renewable source. Similarly at grade rooftop can be ladsscaped with green roof, a huge step forward for mitigating heat island effect & biodiversity in the cities! Other sustainable steps such as rainwater harvesting, etc. can also be useful and potentially serve a community function?
The station entrances will be in close proximity and the catchment of the station will be limited, unless the civic connectivity away from the station box is well developed? The earlier section on the increasing catchment is an important reference.
The at grade station typologies could undergo potential revolution (Particularly for medium capacity systems), if the the rolling stock type changes to longer BRT trains, or battery based (Hydrogen?) rolling stock that can get rid of the dedicated tracks. Where systems are automated, almost L5 self driving (FAO) (Yes operational priority will be given to the trains, but street will be shared with full L5 cars. This future is very near!
The above sketch shows a very simple system that is used presently for LRT or BRT, where minimal ticketing facilities are provided, and passengers are not only able to cross the tracks but arrive at the ends of the platform to access the trains.
However, as systems moves from LRT/BRT to a more medium / heavy metro system, where headway is more frequent, then a common ticketing / concourse space is required. Which will need to be either underground or overground. Both of which have their own merits and needs to be reviewed based on the surrounding built forms. Some points for consideration:
Underground Concourse Cons
More expensive capital cost
Need more mechanical services (HVAC/MVAC)
Enhanced smoke management/mechanical system
Sterilises ground level city utilities
Flooding risk
Overall massing of the system will be higher
Both Capex + Opex higher
Underground Concourse Pros
Reduced visual impact on ground level
Can connect to basement levels of surrounding buildings
Good across the street level connection for general public
Above Ground Concourse Cons
Visual impact on surrounding
Ground level entrances will be marginally bigger
Above Ground Concourse Pros
Can be naturally ventilated
May not need smoke management, mechanical systems
Can connect to surrounding development at podium / upper level
Easier wayfinding for passengers
Footbridge level connection for general public across the tracks
Fire & Life Safety basis for at grade stations generally follows the principles of many underground station life safety principles. It would be prudent to ask why?
Could such typologies not follow local building bylaws.
The answer would potentially be both, no & yes. For larger systems, many local building bylaws lack the necessary classification for station buildings, or many important parameters of building code such as compartment size, escape distances, suppression systems, etc. Hence prescriptive code compliance will end up being more expensive and operationally challenging. Implying that an engineered standards will be better.
Nevertheless, some of the smoke management system may not be required, such as smoke extraction systems. Where possible even the MVAC and HVAC system can also be designed out, which will make the system far more environmentally friendly, as well as cheaper to build and operate.
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