The man, a 47-year-old Reno resident, was taken by medical helicopter to Renown Regional Medical Center in Reno.
Washoe County Deputy Sheriff Deputy Armando Avina says investigators do not know why the man was lying on the tracks. Avina also said it was initially believed the man lost both legs in the accident because of the blood, however the man was missing part of his right leg from a prior incident.
The site is about one-half mile east of the Vista Boulevard exit to Interstate 80 near Sparks.
The man, who survived the accident, told police that one or two others might have been in the area, but investigators did not find anyone else.
No information was immediately available on what the train was carrying or how fast it had been traveling. According to Avina, conductors tried to slow down and used their horn to warn the man that the train was coming, but he did not move.