> Stairs have an optimal rise:run ratio of 7:10.

I think the standard is 7":11" for stair treads...
the rule of thumb is that the rise and run should add
up to about 17.5"

So if you have a 4" tall step the run should be about
13.5" deep so that it feels right to walk up it.

Landings should be 42" deep at least.

Wheelchair ramps shouldn't be more than 1:12 about 8.3%

Standard train tracks never exceed a 4% grade, about 1:24

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