Riding around it creates double track and ruins the trail. If you meet oncoming traffic yield by stopping and stepping aside or leaning aside. Do Not just go around them, this makes the trail wider. Stop, pick up your bike, kick out your track and walk back to the trail. When parking your car use the parking lot.
Cars kill grass with weight and gas.
If the lots full, find another or ride elsewhere. Don't destroy the world we recreate in for our own personal comfort. When camping etc. Don't leave human waste around for others to enjoy. And it ain't sanitary.