Going by what the photos on page 2 show there is clean-ish vertical break about 2-3" in front of the intact weld on the righthand running rail. What we don't know is whether this was the initial break as there is quite a bit of material missing beyond this break, [circa 3/4 sleeper spacing at the top of rail to ~1 sleeper spacing a the bottom], the diagonal break at the far end of the gap suggests that the trailing end end probably wasn't the initial break, it could well have been within the missing material., or if the break occurs near a existing weld, or there are cracks or other defects in the rail, there is a possibility that the hammering caused by a fast or heavy train passing over the defect will cause another break. This increases the likelihood of a derailment. How much depends on how big the overall gap is.
The grinding adjacent to the weld on both rails is not the best most forum members will have seen and on the broken rail the weld appears to protrude above the rail surface, though the photo isn't that clear, there appears to be some material missing from the corner before the weld
Left (intact) Right (Broken)



