So I have been riding Manly Dam regularly for about a year now, and have always believed it was a one way trail. I was out riding on Saturday arvo when I encountered two riders riding up the hill as I was descending (quickly I might add), when I rounded a corner and had to slam on my brakes to avoid a collision. I told them they were riding the wrong way, continued riding, but later on as I was finishing my lap, I encountered them again still going the wrong way.

I suppose what I'm asking is:
1. Am I wrong in saying Manly Dam is one way?
2. Is this common?