Bus trapped by crossing gates.
 

Was the driver 'unlucky'?

http://www.bbc.co.uk/news/uk-england-essex-20164781

I can't tell from the lights.

No! Just bloody stupid!

He was following that tractor much too closely. He entered the crossing not knowing that his exit was clear.

Then, when he is trapped, he just sits there! No attempt to call the signalman! Did he know that the signalman had to check a monitor and, press a "Crossing Clear" button, before the railway signals would allow a train to pass?

My guess is that the lights were already flashing just as the tractor proceeded onto the crossing. Note, the barrier drops just as the rear of the tractor clears the crossing.

Bus driver made the mistake of following too close behind the tractor, and either didn't notice the lights flashing, or thought he had enough time to clear the crossing.

Both drivers should have been prosecuted, but since the tractor probably doesn't have a reg plate fitted, so cannot be easily traced.