According to British law, a pregnant woman can legally relieve herself anywhere she wants. But most importantly, she can, upon request pee in a Policeman's helmet. It is also totally legal to urinate upon the rear inside wheel of any vehicle (this apparently dates back to the days when it was considered the norm to pee on your neighbours cart.
you have to keep one hand on the vehicle though, if you decide to pee on the rear inside wheel of it, otherwise it's illegal. wouldn't want anyone to be arrested for getting the information wrong :) not quite sure how it works for ladies either.