My bike on an incredibly well-built and substantial railway bridge - this is on a
very tiny country lane which sees almost no traffic and about half a mile further on the same lane is a canal bridge festooned with warnings about its weakness and the limited weight it can carry. I can only presume that much greater things were planned for the area when the bridge was first built!
ETA on looking up the history of the line, much greater things were indeed happening in the heyday of holidays in Blackpool, steam trains apparently had
races on sections of the line so I suppose with the amount of traffic on the line it's hardly surprising that they built whacking great bridges over it even on teeny-weeny country lanes.