Why are all the stalls in a public bathroom, except the handicapped stall, the same size? Considering that few restrooms other than those in movie theaters and statiums are ever utilized to capacity, why not build stalls of varying sizes? That way, when the restroom isn't crowded people can use the larger stalls and leave the small ones empty; when more people come in, they late-comers have to use the smaller stalls. Such an arrangement would reduce the maximum throughput of the restroom, but under average usage conditions less of the space in the restroom would be wasted by empty stalls.
The restroom at my work is particularly annoying. There are 10 stalls, and I've never seen more than two in use at the same time. Each stall is so narrow that it's impossible to close the door without standing on the toilet (I'm not exaggerating). Why not remove six of the 10 tiny stalls and replace them with three double-wide stalls? We'd still have seven stalls -- more than sufficient -- and under normal conditions every user would get to occupy a luxury stall. Replacing the 10 tiny stalls with seven equal-width stalls would be another option, but to optimally use the space you want to dedicate an amount of area to each stall in proportion to how frequently it is in use.
It goes without saying that the small stalls should be placed between the large stalls, so as to encourage the maximum amount of insulation between users.