Yes he can save the trains.
If he runs with a speed of 14km/h, he will make the 6300metres in 27 min.
6300metres/(14km/h / 60min) = 27min
In 27 min train A will go 72km and train B will go 54km, so the will be 14km apart from each other.
Train A (160km/h / 60min) x 27min = 72km
Train B (120km/h / 60min) x 27min = 54km