trail riding

I have a lot of friends who like to go to this trail, Duthie Hill, but I wondered why places like Cougar Mountain do not allow bicycles.

I could not find a quick link about this on the King County website (but I only looked for a few minutes). I just wanted to know what the policy was regarding this. I can see both sides of the issue - bikes in parks and bikes not allowed in parks. I just wanted to know what the county criteria was.

Help your park system out! Volunteer!