Since the choice is between riding the bike on the service road, or driving the car, I vote for using the service road. I don't use one myself, but the benefits I get from bike commuting are great enogh that I would if that was the only way to keep riding. As you get more into commuting, you may find that you are ready to take the detour. If not, no worries. If it were me, I'd ride the service road, over driving the car.