Complex sentence: The Site occupies accessible via car only by private road, so advance reservations are required to visit: private vehicles are not allowed, and transportation to the park is provided by a twice-daily free shuttle from Danville, Wednesdays to Sundays.
Split into simpler sentences: The Site occupies accessible via car only by private road, so advance reservations are required to visit. Transportation to the site is provided by a twice-daily free shuttle from Danville, Wednesdays to Sundays.