I know your pain.
If the car in front hasn't cleared the barrier almost immediately, I stop and leave a big "reversing space". Of course, you get the occasional wazzock nipping in front only to confront someone backing out.
I have to go through 3 gates on my daily commute (one going in, two going out).
On the way home yesterday, I got two RoS (one at each gate). Grrr.