Sideloader restraint?

[Safetyranger]

I am looking for some info on seatbelt requirements for a multidirectional electronic sideloader. We require forklift operators to use seatbelts and these lifts don't have them. The design is significantly different from a forklift truck and the risk of falling out is nearly nonexistent. This is a fully enclosed cage with the seat apparatus being the door/entry point. This is closed at all times of operation and has an interlock system that shuts down the lift if the latch is disingaged. Every standard I have found refers to open sided sit down lift trucks. Does anyone know of a standard that refers to this type of specialized vehicle? We need to know if it will be necessary to add seatbelts to these lifts. I have included a link to the sideloader manufacturer for design questions.