I went and hiked Fountainhead a few weeks ago. At that time the gates were closed and you couldn't park in the parking lot, but lots of people, including me, parked on the access road leading to the gates. If nothing has changed, you should be able to park there and bike past the gates into the park. I hike Prince William Forest a few days ago and it was the same - gates closed but the park was accessible. They had a sign out saying the park was open with minimal services, which means you have to hoof it in to the trails. It seems that what they're doing is limiting access by vehicle, but declaring the parks to be "open." Its a stupid policy to prevent access to the parking areas because the secondary consequence is that people are parking outside the parks in areas that create more safety issues.