Blurred Photos When Using Tripod

Thank you for the replies.

To be fair, it was only a light (cheap) tripod - as I was carrying it as hand-luggage on the planes. That said, it has usually been ok as I have taken many photos like this in the past. The railway vehicles at the time the exposure was taken, were not moving. The only change in the set up was the lens.

In future, I will try with IS switched off...