That's a hard one. Driver of the artic may have either not been aware of, or underestimated, the overall length of his load. On the other hand, he may have been very unlucky, crossing the railway but then getting stopped at the traffic lights situated after the crossing. Either way, his trailing load was still obstructing the line, and neither he, nor the train driver, had anywhere to run.
The insurance claims are going to be interesting, not to mention the eventual accident investigation report.