In exchange, passengers should get accustomed to a different way of sitting that's more like a semi-upright perch.
PriestmanGoode's proposals come after a summer of discontent in the UK that saw trains filled to 200 per cent capacity and opposition leader Jeremy Corbyn make headlines when he was photographed sitting on a crowded carriage floor.
Studio head Paul Priestman told Dezeen that given the overcrowding on public transport systems around the world, it was time to "re-evaluate sitting".
"Seats have been like this on trains for hundreds of years and it's time to ask, are they fit for purpose anymore?" he said. "I think we need to re-evaluate sitting."
"Our design just allows more people to get on the trains, and the old conventional seating takes up so much space."
PriestmanGoode – which is also working with Transport for London on its next generation of tube trains – has proposed two new seating models, titled Horizon and Island Bay.
The lightweight Horizon features rows of narrow seats that are closely packed together, while Island Bay has more conventional seats that fold up to create standing space at peak times.
However, Horizon has been carefully designed with an ergonomist to ensure its slim seat offers passengers full support so they can take the weight off their feet.
While it fits four seats to every three currently in the average train carriage, neighbouring seats are staggered so as to increase shoulder space between passengers.
Video showing PriestmanGoode's Island Bay seating design
Each seat has a small foldaway table with grooves that support tablets and mobile devices.
Priestman believes that this kind of seating could also be preferable for health reasons, since "sitting is the new smoking".
"Sitting back for an hour's journey, do you really want to take up that much space if it's not necessary?" he said. "As soon as you can lean, then you can actually do something on your tablet."
"You look at young kids, they don't sit down – they lean, they prop, they lounge."
PriestmanGoode's other design, Island Bay, offers traditional seating for some journeys, although it encourages most passengers to stand at peak times.
It is based on the model where four passengers sit facing each other around a small table. It also fits in one additional "seat" at the end of each bay, with a padded backrest giving standing passengers something to lean on.
This flexible design would create 15-20 per cent more seats and increased standing capacity. The layout is more social in character and can also accommodate wheelchair positions.
Developed with funding from the UK's Rail Safety and Standards Board, Horizon and Island Bay can be installed on new or existing trains, trams or buses – which according to PriestmanGoode means they could be in circulation within a year.
The studio envisions operators using a combination of these seats alongside their regular offering. Horizon and Island Bay are being manufactured in the UK by Transcal, which is taking orders from today.