Question: Couldn't Dewey have just stopped the train, backed it up, and then changed the switch instead of hopping out of the cab?
Answer:He would have been able to, although he would have lost a considerable amount of time in doing so. However, the film was based on a true story where the engineer of CSX 888 noticed a misaligned switch and saw he wouldn't be able to stop in time, so he decided to get out of the cab to align the switch. He thought he set the locomotive up properly to make it safe to get out and back in, thus avoiding the need fully to stop and then back up. So it's not really a matter of what Dewy could have done differently since they were just following events has they had already occurred.
Answer: He would have been able to, although he would have lost a considerable amount of time in doing so. However, the film was based on a true story where the engineer of CSX 888 noticed a misaligned switch and saw he wouldn't be able to stop in time, so he decided to get out of the cab to align the switch. He thought he set the locomotive up properly to make it safe to get out and back in, thus avoiding the need fully to stop and then back up. So it's not really a matter of what Dewy could have done differently since they were just following events has they had already occurred.
Bishop73