Complex sentence: The first of his steel rails was sent to Derby Midland railway station, where it was laid down at a particularly heavily used part of the station approach where the iron rails had to be renewed at least every six months, and occasionally every three.
Split into simpler sentences: The first of his steel rails was sent to Derby Midland railway station. They were laid at part of the station approach where the iron rails had to be renewed at least every six months, and occasionally every three.