So, I have put together a few images explaining the design of BMD and why they went for a reduced seating capacity.
It is fairly common knowledge now that rail seating will be installed at BMD in a number of areas, up to 3 have been mentioned at some point or other. There was also mention in a number of places about Dortmunds Yellow wall. This reference was less about the size, than it was the strategy. The 'seating' at BMD is designed like this
View attachment 138987
Notice the double step, that allows somebody to stand behind the person in front and maintain a view. That means that we could double the rows in the ground (almost, a person standing takes up more width that a person sitting, ever notice how its more cramped at half time and people spill onto the walkways....)
Many older stadiums have been designed and built under different regs than the new stadiums, such as Spurs, BMD etc, and the regs allowed more people per facility. When the all seater stands were mandated, in all cases the capacity came down, and facility provision per person improved, meaning that every available space could be taken by a seat, regardless of regulations at the time. The result was that concourses were deemed suitable for full seated capacity. There will be no appetite to decrease provision per person as it would now be in direct contravention of current regulations. Hence, old stadiums will not be able to install rail seating beyond 1:1 (with the increased width of a standing person being larger than one seated, it may only be 0.8:1 for standing versus seated, based upon blue book guidance and minimum measurements.)
This image show a concourse designed to balance maximum seating, such as at Spurs.
Spurs was a funny case though as they also gave large parts of their stadium to NFL usage (Massive changing rooms etc. pushing other facilities elsewhere and reducing concourse space. A massive balancing act.
View attachment 138991
Whereas the following two show the design at BMD, over provisioning for the seated arrangement, allowing a capacity to be raised during standing. All within the same boundary constraints
View attachment 138992
View attachment 138993
The images above are based upon a 1.6:1 ratio, purely cause it worked easier on powerpoint.