Yeah that happens when the track is closed. Usually they close it when a bad accident happened or a vehicle lost oil/fluids. In the webcam picture you can see cars lining up on the track. Those are the cars that have a ticket for another lap..they just finished one and are waiting for their next one. They are parked there however because... yup.. the track is closed
A looooong long time ago (2 years ago lol) you had to start your next lap (if you have another ticket obviously) by exiting the track. But because the parkinglot and the traffic exiting the parkinglot to the entrance is VERY crowded at times, traffic would completely jam/stop.. so now you can stay on the track if you want to do another lap. Brrr bad English, hope you understand.
Anyway, there were 3 big closures today. 1 totalled Vectra, 1 totalled GT3, 2 totalled bikes and some little damages here and there. Just another Sunday.