You're comparing apples and oranges, old fella. While driving coaches is arguably more risky than flying an airliner. Is it more risky than flying a twin turboprop into foggy airports all winter? That is the more apt comparison.
The reason airline flying is safer is because the aircraft are designed to be as safe as possible, pilots are trained to a high standard and consistently have to prove their competence and the rules are designed to ensure maximum safety.
Coach drivers on the other hand well.............frankly why are we even having this discussion? It's insulting.
When coach operators and drivers are subject to the same standards as aviation, it will be safer.
Remember too, the average regional/commuter pilot will be on less money than a coach driver. Which job is more risky?