TULSA, Okla. (AP) -- The driver of one of two freight trains that collided in the Oklahoma Panhandle last year, killing three railroad workers, had complained that he couldn't distinguish between red and green signals, an investigator told the National Transportation Safety Board on Tuesday.
Dr. Mary Pat McKay was among several investigators presenting evidence to an NTSB panel in Washington charged with determining the cause of the June 24, 2012, crash near Goodwell.
Inspectors said signals warned the eastbound train to slow down and stop at a siding so a westbound train could pass. The westbound train slowed down, but the eastbound train did not, roaring past the siding at 68 mph and colliding with the oncoming train.
McKay told the panel said that driver of the eastbound train had suffered from glaucoma and cataracts, and that from 2006 to 2009 he complained about the deteriorating vision in his left eye.
"He repeatedly complained that his vision fluctuated and was described as OK one day, not OK the next," McKay told the board.
The panel voted 5-0 that the train operator's failing eyesight was the probable cause of the collision.
The Federal Railway Administration does not require comprehensive medical screening, instead relying on operators to report medical conditions to the company, McKay said. Since 2009, the driver of the eastbound train had undergone 12 separate eye procedures and complained that he was having trouble reading train signals. Doctors diagnosed him with protonosis, in which red and green are perceived as a shade of yellow, she said.
"Had the railroad tested the eastbound engineer's vision in 2010, medical records demonstrate that he would have failed ... any of the standard color vision tests," McKay said.
Deborah Hersman, NTSB chairman said the company is responsible for ensuring employees are capable of fulfilling their roles safely.
"Railroads must pay extra attention to monitoring employees with chronic medical conditions who hold safety-sensitive position," Hersman said. "If an employee can put their life or the lives of others at risk, it is imperative that others take the necessary and appropriate action.
A Union Pacific spokeswoman, Raquel Espinoza, said company records "indicate the engineer passed all of the federally mandated vision tests and suggestions that his vision may have contributed to the accident are pure speculation."
Another investigator said controlling trains remotely, through a system known as Positive Train Control, rather than relying on train drivers to read trackside signals, would have eliminated the possibility of an accident that day.
Tim DePaepe, who attended the accident site last year, said Positive Train Control would have presented visual and audible warnings to the engineer and crew that the train was in trouble. If warnings are ignored, the system applies brakes automatically.
"This accident would not have occurred," DePaepe said.
Inspectors recovered no recordings of crew communications and couldn't perform autopsies on those who died. A westbound crew member survived by jumping from his train before the accident.