The incident happened at Commonwealth and Base avenues just after 2 p.m.
Police say a man in his 80s ran a red light and was hit by another vehicle, which pushed him through a chain-link fence. The man continued to roll through an empty lot and went through a second chain-link fence before ending up on railroad tracks.
A group of people, including two city of Fullerton maintenance workers, rushed over to help.
"The door was open in the vehicle and that's when I noticed a man," said Hector Encinas, one of those two workers. "He looked like he was in a daze. I pulled off the belt buckle and asked him if he could support himself on his legs. He said he couldn't feel his legs at that time, so I helped him move his body and pulled his legs out of the vehicle."
The man was moved to safety. Rescuers said the train hit the car within five minutes.
None of the 200 passengers on the Amtrak train were hurt.
The man's Cadillac DeVille was totaled.