why do gas stations have one way lines at the gas pumps?

Question

and are there any traffic rules about what the direction should be in relation to the road that runs alongside the gas station pumps

Answer 1

it is just to be a convience to the purchaser. Costco has a one way system for their pumps. Everyone enters the same direction. Hoses on both sides of the pumps.

Answer 2

I have worked at 2 gas station and I can say for a fact this is not always the case, if ever that i've noticed. In fact different cars have the gas tank on different sides so it would be impossible to force lanes, because some cars would not be able to fill up.