Morality is much broader than religion. A non-religious culture would have a moral guideline based on it's view on what is wrong and right. Likewise a non-religious philosophies have systems of morality. Religion is one driver of a societies morality although there's some chicken and egg questions in there (ie: is religion merely parroting a cultures pre-existing moral views). Laws, as I see it, are mostly attempts to codify a societies morality so that it can be enforced centrally and systematically instead of piece meal and locally.

Any system of morality in which it's morally wrong to endanger the lives of other motorists is a system of morality in which a justification for traffic laws can be constructed.

(Also, I find your juxtaposition of atheism and morality very alien. I say that as an atheist with strong opinions on what is or is not moral.)