A favorite song performed by the Western swing band Asleep at the Wheel (among others) suggests that you can "get your kicks out on Route 66." But there's no thrill for the millions of motorists who may be navigating interstates alongside long-haul bus and truck drivers who are having trouble staying alert.

Investigators suspect that commercial drivers involved in a number of high-profile crashes on the nation's highways had medical histories that should have kept them off the roads - that is, if they had been up-front about their health woes with their employers and federal transportation officials.

A recent CBS News investigation found hundreds of instances in which crashes were linked to drivers' health issues, particularly sleep disorders and vision problems.

A University of Minnesota study released in March found that truck drivers whose sleep is interrupted by a breathing condition known as sleep apnea are much more likely to be involved in a wreck if they aren't properly treated for the condition. The study looked at more than 1,600 U.S. drivers with sleep apnea and calculated that their risk of crashing is five times higher than that of other drivers. With good reason, the findings prompted a call from the American Academy of Sleep Medicine for "transportation companies to implement comprehensive sleep apnea screening and treatment programs to ensure that truck drivers stay awake at the wheel."

Commercial drivers already are required to pass health screenings every three years under U.S. Department of Transportation rules that, since being tightened in 2014, have removed a reported 70,000 drivers from the roads. But the screenings clearly need to be fine-tuned to deal with drivers who, knowing that full disclosure of their health issues could sideline them, might avoid acknowledging certain medical concerns.

Law enforcement and transportation officials could also focus policymakers on the issue of high-risk drivers by more clearly documenting instances in which health conditions play a role in crashes. The CBS report found that few states compile such information.

It's not clear what caused a tractor-trailer and a car to collide on the Pennsylvania Turnpike in Bucks County last week, taking the life of a Moorestown college student, but it was a terrible reminder of the heightened danger of collisions involving commercial vehicles. With widespread distraction by smartphones further compounding the risks to all motorists, it's that much more important for bus and truck drivers to be wide awake behind the wheel.