"I see no reason to claim both shouldn't apply unless the earocar was not supposed to operate on roads. If a vehicle is going to fulfill the role of another type of vehicle it should meet the safety standards for that vehicle. "
Exactly so, it's reasonable, and therefore we can't buy a vehicle for a fairly reasonable price that can fly and would also probably get about same or better gas milage as a Hummer.
It's also reasonable that passenger traveling on a sub-orbital "airplane" should have about same level of safety to themselves and others that a normal airline would provide, and therefore we won't have sub-orbital travel either.
And if you continue with this line of reasoning, we certainly can't go to the Moon or Mars- that will be a task which needs to be left to the million dollar robots (and if we get AI, then we are *really* in trouble:)

How "they" still allow people to ride motorcycles is a real wonder- I suppose outlawing them will come later. First, of course you are going to need to get rid of those Hell's Angels, cause they like their hogs and would stomp all over any twit that tried to inferfered with what they liked to do.