MTA Announces Sleep Apnea Testing for Conductors and Engineers Systemwide

— -- After multiple train accidents in recent years were linked to sleep apnea, the New York's Metropolitan Transportation Authority (MTA) has announced it will be the first public transportation agency to test conductors and engineers on all its train and bus lines for sleep apnea.

Commuter and subway train crashes across the east coast in recent years have drawn attention to the sleep condition. In 2014, four people died after a Metro North train crashed in the Bronx borough of New York City. The cause was later determined to be the the train engineer's sleep apnea. Last year, another engineer reported having the condition, according to the Associated Press, after the train he was directing crashed into the Hoboken station in New Jersey, killing one woman.

People with the condition may not realize the effects of being sleep deprived, Dr. Samuel Friedlander, a sleep specialist and assistant clinical professor at UH Cleveland Medical Center, told ABC News.

"I don't think people realize how problematic being tired is because we get used to it," Friedlander said. "I think what the MTA is doing is a win-win for both employee s and the citizens of New York City."

The MTA already required Metro-North train engineers be screened for the condition. Yesterday it announced screening and possible treatment would be expanded systemwide to all train engineers and conductors, as well as bus operators.

"Safety is our top priority and MTA is going further than any other transportation agency in the country to prevent the risks of apnea. With this proposal, we are not just working to implement industry best practices, the MTA is defining best practices," MTA Chairman and CEO Thomas F. Prendergast said in a statement. "Sleep apnea is a serious illness and treatment will improve the quality of life for those who have it, and help them live longer."

The screenings will include evaluation of a person's body mass index, neck circumference and sleep patterns. At-risk employees will undergo further testing and possible treatment.

Sleep apnea is a common sleep disorder that causes a person to have shallow breaths or pauses in breathing during the night. Depending on the severity of the disease, it can cause symptoms that wreak havoc on normal sleep patterns, causing people to feel groggy or tired during the day.

Sleep apnea can occur for multiple reasons. The National Institutes of Health says half of known cases are related to being overweight. Snoring is the most common symptom, but morning headaches, memory or learning problems, feeling irritable and dry or sore mouth are also signs of having the condition.

ABC News' GIO BENITEZ, GEOFF MARTZ, GERRY WAGSCHAL, STEPHANIE WASH and CONOR FERGUSON contributed to this report.