From trains going off the rails to buses crashing on the road, tonight we're investigating a common cause of accidents. It has to do with sleep. We're not just talking about tired drivers. The problem... See More
From trains going off the rails to buses crashing on the road, tonight we're investigating a common cause of accidents. It has to do with sleep. We're not just talking about tired drivers. The problem could be helped with a proper diagnosis. So why is there still accident after accident? Here is our series "Nightline" investigates. Every day, millions of passengers put their lives in these people's hands. But what happens when they fall asleep at the wheel? Watch this actual video shot on trains, trucks, buses, even school buses. And the aftermath can be devastating. Some of these accidents like this one today may have been caused by simple fatigue. But others caused by a medical condition that it turns out is easily diagnosed and treated called sleep apnea. Sleep apnea causes the windpipe to constrict during sleep, waking you up temporarily and preventing deep sleep. Older people and overweight people are at higher risk. We are concerned because that means there are people out there that have sleep apnea unidentified that are operating a vehicle in all modes of transportation. Mark rosewind from the national transportation safety board says this is a national problem. We have accidents in rail, commercial trucking, commercial aviation, marine, pretty much every mode of transportation. One of the worst train accidents in the U.S. Happened last year in New York on metro north. Four died, 63 were injured. Among them, former New York cop Eddie Russell. The glass windows in front of me was breaking. And still oh, this is not happening. I'm going to die. This is what I think to myself. The cause of the accident? The metro north accident is interesting, because we now have factual information that the engineer in that accident had sleep apnea. So with accidents being caused by a condition that is easily diagnosed and treated, why aren't our nation's train operators, bus drivers, pilots, and truckers being tested? I think safety is more important than anything. If they don't rectify the situation, it could happen again. In some cases, they are. Some companies like prime, a trucking company, are stepping up to the plate. Prime has its own sleep lab to screen its drivers. But so far there are no nationwide rules from the fmcsa, which regulates trucks and commercial buss to require this. One of the biggest problems with that is many of those people don't know they've got it. We decided to go find one of these drivers. This one, seen here falling asleep in her school bus full of kids. I felt like there was my baby, you know. Precious cargo. I know I was responsible for getting them to and from school. Daesha clay says she doesn't remember what happened that day. No, I don't recall falling asleep. Ever? Never. She was fired immediately when this video became public. But she was never tested for sleep apnea, before the accident or after. So we brought her to Carolina's health care system in Charlotte, North Carolina, for a test. Very nice to meet you. Nice meeting you. If I do have it, I will be a mixed feeling. I'll be happy to know, because then I know what to expect and what I need to do. And then also confused. Like, if I would have known before, I don't think I would be in this situation. It's going to pick up snoring on the the computer. It's an overnight test, and all night she sleeps, she is being monitored. Good morning. How you? She gets her diagnosis the next day. Essentially, you stopped breathing roughly seven times an hour. That's mild sleep apnea. I would like you to try a therapy. And we have a machine called a c-pap. The thing about the people who don't know they have sleep apnea, it's scary, because honestly, some people do not know. For example, like me. I did not know. I didn't have no clue. In my opinion, I feel like there should be a wide testing when it comes to transportation. But the ntsb says their recommendations for national testing of train operators, school bus drivers, truckers and pilots are not being acted on fast enough. When the ntsb investigates, we try to make recommendations so horrible crashes don't happen again. So we're going to tell agencies you have to address sleep apnea. We asked the department of transportation to do an interview, but they declined, giving us a statement, saying D.O.T. Is committed to ensuring all train operators, truck drivers and pilots are fit for the job and receive the treatment they need to combat sleep apnea. But remember, there are no nationwide rules to require drivers of trains, trucks or buses to be tested, even if they are high risk. Critics say these rules are taking way too long to develop. Okay. The D.O.T. Is not talking, but what about the executive vice president of the trade association representing owner operator independent drivers? Surely he would want this testing, right? I think the ntsb is just saying this is what caused the accident. I think that's junk science. Todd Spencer says he is not convinced sleep apnea is a real cause of accidents. Generally, what somebody is saying, that we're killing people, we're killing people. They have an economic interest in pursuing this. Either they make money from treatment, they make money from diagnosis, they make money, maybe through lawsuits. The ntsb tells us it's one of the biggest problems is that these people don't know they have it. We've not seen the impact in safety in health that they talk about. Do we see it play out in terms of impacting highway safety? No, we don't. And Spencer, like many of the players in this battle, worries about the cost. Just the cost of doing that test is over $2600. It's a pretty big piece of change. But rosekind says there are alternatives to hospital tests. There is testing that can be done at home. And literally, at a few hundred dollars. And it's not like medical testing is the only solution there is new technology that could help keep the public safe, if only it were installed on buses, trains and trucks. So what we're going to do is demonstrate city safety, it's a low speed autonomous braking system. Drive straight towards the vehicle, no brakes. I went to see some of the devices firsthand, already available on many higher end cars. Okay, here we go. Devices that can brake to avoid a collision. I'm trusting it. No brakes, no brakes. Wow. And alert a driver who starts to nod off. If you are falling asleep, the idea is that that driver alert system will just sort of light up and you'll hear a sound. Here we go, driver alert. Technology will never stop crashes from happening. Spencer of that independent trucking association may be dubious, but the ntsb says these high-tech solutions, some of which are just beginning to be available as optional extras on trucks in the U.S. Hold promise. We specifically have looked at some things in rail and trucking, and have made recommendations to find innovative technologies that could make a difference in alerting a driver to their fatigue state. The department of transportation says one of its agencies, the fmcsa has begun research that could one day lead to sleep apnea regulation under a law president Obama signed just last year. Meanwhile, accidents like this continue to happen. This should be some type of test so nothing like this ever happen again. For "Nightline," I'm gio Benitez in New York.
This transcript has been automatically generated and may not be 100% accurate.