More than half a million tractor-trailer and bus drivers who have commercial licenses also have medical conditions that qualify them for full federal disability payments.

That's just one startling fact in a new safety study obtained by The Associated Press.

Every year hundreds of deaths and injuries are blamed on commercial truck and bus drivers who suffer medical emergencies while driving vehicles sometimes weighing over 40 tons.

An AP review of federal records finds that truckers violating federal medical rules have been caught in every state.

The federal agency that oversees truck drivers admits it hasn't completed any of eight recommendations safety regulators have proposed since 2001. One would set minimum standards to determine who is medically fit to drive commercially. Another would prohibit "doctor shopping" to find a physician who might overlook a risky health condition.

A Florida bus driver who will figure prominently in a congressional hearing this week suffers from lung disease and uses three daily inhalers to control breathing. He told congressional investigators he "occasionally blacks out and forgets things." His commercial license expires in 2010.