if the supervisor runs to the manual switch that is 6.300 metres away with a speed of 14 km/h he will be there at 27 mins.
train A in 27 mins will be managed to cover 72 km with a speed of 160 km/h.
train B in 27 mins will be managed to cover 54 km with a speed of 120 km/h.
that means that trains will be already covered the distance of 126 km between them and the wiill still having 14km remaing distance to each other from the 140 km that they had in first place.
So yes the supervisor will manage to stop the accident and save the trains!!!