Unsafe at any speed?
Actually, we own a F150 (full disclosure here: we live in the country and its a must for the Hobby Farm because you can't get really get the farm supplies delivered anymore). When my youngest son took his scooter permit, the instructor doing the practical training asked me if I could park it in a specific spot. He then put a scooter about 40 feet ahead of it and had all the kids alternate from being on the scooter and looking back in their mirrors and in the cab in the driver's position - from which they could barely see the top of the helmets of the scooter riders.