You will aways find exceptions (like emergency and medical sercices, transporting people who cannot walk or bike, transporting goods …) that’s why I said “most of the time”. A park ranger (edit : I meant " could use") use a car for her/his duties and go back home to her/his personal business with public transport. Most situations could be handled without a car, and the few left could be handled with much smaller vehicles (and should be looked at to minimize the use of car to a maximum. I’m sure a ranger could do some of her/his job riding a dirtbike)