Does anyone know the actual dimensions of the Superliner's stairway. I know it's tight, but what is the actual size.

I am thinking of using my AGR points for an award, but I'm debating if I can get a bedroom (upstairs) or an acccessible bedroom (downstairs). My sister uses a walker (which can be folded up) will be accompaning me. (She can climb the stairs, and I could carry the walker.) I know that I could leave the walker in the storage area, but that area is unsecured. And I prefer a room upstairs, both for comfort and ease to reach other cars.