I think being able to research a vehicle such as a quad bike (ATV) would be a neat way to allow staff to travel faster through the park, on top of this the addtion of staff road ways would allow staff to drive out of site. I believe you could also implement a system where staff will only use the ATV if it's a long journey away from the staff centre or on the other side of the park. A jeep could also be researched after the ATV , this could be a multiple staff transport vehicle that would allow multiple staff members to move around the park at once.
I believe making it so breached or escaped assets of large sizes could also attack a vehicle if it enters its general area.