When a rail breaks, is it usually verticle, or can it be horizontal and crack just under the railhead?
I have seen where the railhead was broken and was off ( missing) about a 15 inch section. but this is not as common as the vertical breaks. traffic was stopped until this rail was replaced.
Rails will break any way the stresses in the rail dictate. Head, web, base and in any combination and direction.
Of course, some of the stress factors are more numerous than other, and as I’ve seen, the ones to cause vertical breaks seem to be the most common (esp. at weld points?)
Often flaws in the steel will dictate how it will fail. Wear can cause a head to mushroom and then the flange can break it off. Some yard rail is not for the faint of heart. I wish I could get by with some of the things the prototype can. It would make track laying a lot easier.
Head-web separation…typically caused by a mill defect, piped rail (steel worms!) or poor railhead design (like some old 110# rail)…
Rail can fail for a whole host of internal and external reasons. Flat wheels, broken wheels and cat-tracks for instance, can nick a railhead and do-in miles of railroad. If a railcar comes into a yard with a broken wheel, the track forces will be out looking at the rail and frogs in search of nicked rail. The surviving two or three US rail mills have learned so much over the years about metalurgy and service issues that the failures due to mill practice have dropped significantly. There are still failures (like the legendary Bethlehem 136 CWR headaches on Tehachapi 15 years ago), but they are few.