Mammoth Cave Railroad Bike & Hike Trail Gravel trail is not ideal By uncleho in 4/8/2012 11:37:58 PM | Adults can ride the trail, but the youngest of children will have problems. Not only did our child crash on the loose gravel, but it made it quite hard for her to just climb hills. We saw other kids crashing. The choice of loose gravel was poor. Crushed limestone or similar would have been a far better choice. We ended our ride early and chose to hike the trails, which were beautiful.