Igor Bensen claimed that the B-8M was "roadable." I suspect that the DMV would disagree. Never mind lights, let's start with that murderous open propeller.
I had VW engine trouble in my first gyro all the time. Once, I landed on a residential cul-de-sac with the engine still running, stopped at the stop sign at the intersection with the main road and tied off my blades with the belt from my pants, then drove the gyro back to the airport. That doesn't make it legal or safe, though.
The issue with "roadable" aircraft is the same as the issue with combination tools ("It's a crescent wrench -- it's a screwdriver -- it's a can opener..."). The design goals for the items you're combining are seriously at odds with one another. You end up with a flimsy car or a heavy pig of a plane... or, heaven forbid, both.
Like a cross between a dachshund and a great Dane, some hybrids just weren't meant to be.
A plane or gyro that can self-propel down to the airport using a low-power drive to one wheel is perfectly possible. It just won't really be a car or a bike -- simply an aircraft that can taxi safely on the streets for a short distance; a big moped. It will be too flimsy to go fast or tolerate rough roads.