I'm thinking of bicycle as lower cost alternative to using a vehicle and an opportunity to getting paid while exercising. Yes, bicycles should be ridden on the streets, however, the bicycle would be slightly closer towards the sidewalk but it should not make much of a difference with the cameras and GPS. I definitely agree with you on using a bicycle on bike trails, whether on or off-trail, which can not be accessed by vehicle. It can sure be implemented into bicycle computer with GPS to help the rider find a bike trail.A bicycle is a good idea, but aren't bicycles supposed to be ridden in the street? In that case, they're already using cars. In some places like hike/bike trails, that would certainly be a good option.
What kind of scooter? Moped or mobility scooter? A mobility scooter could certainly be driven on the sidewalk.
A gas powered scooter is great on gas mileage and would cover a larger area quicker than on foot.