Spyke wrote in message ...


"According to sources at the crash site the incident was caused by a
broken rail, and a member of the rail staff who saw the rail said it was
"rusted" before it fractured."

Out of curiosity (and I accept there may be a perfectly good answer to
this), how can you tell a rail is rusted just by looking at it? Being
steel there's always going to be a fair bit of corrosion on the outside,
with only the tops being polished clean by passing trains.

Quite right.
There's almost always some corrosion on rails (identified by the
typical orange colour, normally in the web of the rail). In very
unusual circumstances (less than 1 in 1000) pitting from corrosion can
lead to a rail defect/break. It takes close inspection by an expert to
spot the spot.
Rails are tested ultrasonically at regular intervals, and should
identify the defect - a small crack in the rail which will eventually
grow until it becomes a rail break. It takes quite a while for the
crack to grow (months, even years) - testing is every 2 months, to
pick up cracks before they become breaks. It is concerning that the
break occurred, since the testing regime should have prevented this.