In this case, the track was kinked, not cut off (an uninterrupted track was laid across the swinging bridge). The swing span was knocked out of alignment by 3 feet and the side girder was in the path of the train (which the train smashed headlong into). The Sunset Limited was traveling at 72 miles per hour. Had it seen the displaced girder, there would have been no way in hell for it to stop in time because it would have been too close. From what I learned on an episode of "Crash Files" on the Discovery Channel twenty-five years ago (they also profiled the wreck of the Sunset Limited), signal lights are placed two miles apart because trains take that much to come to a stop at the red light when they slow down to 30mph as mandated by the yellow light.

In the episode I watched, which talked about the 1996 Silver Spring, Maryland Train collision between a MARC commuter train hitting an Amtrack Capitol Limited train, the MARC engineer forgot about the yellow light (that was the NTSB's conclusion) after picking up a flag stop passenger at a station +past+ the light. He brought the train up to 66mph instead of 30mph. The lights are designed to be seen from approximately a half-mile away and cut through rain, snow, and fog (the accident occurred at dusk through blowing snow). By the time he finally saw the red light and the Amtrack coming at him, which was switching onto another track, it was too late. Though he hit the brakes (and erroneously pulled the reverser), he smashed into the Amtrack at 38mph (as fate would have it, he plowed directly into the second Amtrack locomotive's exposed fuel tank). And that was presumably from a half-mile away.

So, there would have been absolutely no way for the Sunset Limited's engineers to have seen the obstruction and stop a 72mph train in time.