The following comes from the PA DMV website....
"PASSENGERS IN AN OPEN-BED TRUCK
An open-bed pickup truck or open flatbed truck may not be driven at a speed of more than 35 mph, if any person
is occupying the bed of the truck. Such a truck may not be driven at any speed, if a child under 18 years of age is
occupying the bed of the truck.
Exceptions to this law are:
• A child of a farmer, who is being transported between parts of a farm or farms owned or operated by the farmer
in order to perform work on the farm or farms.
• A child employed to perform farm labor, who is being transported between parts of a farm or farms owned or
operated by the child's employer or employers.
• A child possessing a valid hunting license, who is being transported between a hunting camp and a hunting site
or between hunting sites during hunting season.
• A child, who is a participant in an officially sanctioned parade, only during the course of the parade."
The only other law states that passengers may be hauled in a 5th wheel trailer if there is a means of electronic AND visual communication between the vehicle and trailer.
Better too far back, than too far forward.