While the dangers of falling asleep at the wheel are readily apparent, the scope of the problem is not fully appreciated, some transportation insiders say.

Fatigue is highly underreported as an accident cause, said Daniel Bongers, chief technology officer at SmartCap, an Australian company that makes industrial safety products. For example, he said, a crash might officially be attributed to roadwork, but fatigue may have slowed the driver's reaction time and decisionmaking.

Juan Ochoa, an 18-year veteran of long-haul trucking, agrees. He believes most accidents are caused by fatigue. "I'd estimate 70 percent," said Ochoa, who manages a fleet of 80 trucks for National Transportation Services in Kent, Wash.

Help finally might be on the way. Technologies are becoming available to alert drowsy drivers, sometimes even before they feel tired.

Biometric sensors are getting lighter, cheaper and more accurate, and new software systems can connect driver and vehicle data. New wearable technology monitors come in a variety of forms, including caps, vests, wristbands and glasses.

The sensors can detect head bobs and jerks, signs the driver is falling asleep. But they're also capable of much more sophisticated monitoring,

For instance, SmartCap Technologies makes a headband that detects electronic brain waves and translates them to a measure of alertness or fatigue. It notifies the drivers if they fall into the drowsy range.

Glasses made by Optalert measure the driver's eye blinking with an LED light monitor. Eyelids that stay down too long might point to a sleepy driver. The real-time measurements are displayed on a dash-mounted device with alarms and notifications.

A headset made by Maven Machines detects if a driver is looking forward through the windshield, up, down or sideways, and measures mirror checks, which can decrease in frequency if a driver is getting tired. This system also delivers audible routing, weather and other information, such as the speed limit.

The software behind these devices is complex, with data from a variety of sources, said Craig Campbell, vice president for marketing at Maven Machines. One challenge for manufacturers is figuring out what constitutes too much information.

"It's easy to drown in a sea of data," so driver-monitoring systems must pick out the important events to report, Campbell said.

The alerts sent to drivers are meant to encourage them to find their own best way to get back into a more alert state, such as stopping and walking around or having a snack, Bongers said. The hope is that as drivers get feedback, they'll start to recognize their own drowsy warning signs.

There's even technology being developed to help drivers when they're not driving. Software sold by Fatigue Science analyzes sleep data for long-haul truckers, using data from wearables to measure the quality and quantity of a driver's sleep, plus their sleep history or sleep debt. It is intended to be a predictive tool, forecasting when drivers will get tired so they can pull over and rest before that happens.

While great strides are being made with self-driving vehicles, it's likely still going to be several years before they are commonplace, said Karen Levy, an assistant professor in the Department of Information Science at Cornell University. In the meantime, the monitors could save lives.

"We're going to need an alert human [driver] for the foreseeable future," she said.