The expectation is that, if able and willing, persons are expected to exit their mobility vehicle. When a stroller with a child old enough to exit and walk through the scanning device on their own approaches, parents are told that everyone needs to pass through the scanner. At that point, they typically tell the kids to get out and everyone walks through. This frees the security staff to inspect the stroller (they are instructed to NOT reach into the bottom of a stroller with a child in it). The point is that the mobility device must be inspected. If the child is unwilling or unable to exit, parents are told to lean the child forward in their seat to reveal anything behind them, and then asked to pull everything out of the storage area in the bottom of the stroller. With scooters, most folks are able to briefly exit and walk through the scanner on their own. If not, supervisors are specially trained to walk them through some steps to allow an inspection (of their person) while seated in their scooter. Parents typically grab infants and carry them through the scanning device, but honestly, in my experience, very few infants are brought into the parks. The security host/hostess' job is to ask the question (sir/ma'am, are you able to walk through the scanner on your own). If not, the alternate process is done (security supervisor performs an inspection). Mobility devices do NOT go through, hence the policy.