Add alcohol or drugs and it gets worse.
Car vibrations make drivers drowsy in just 15 minutes and could seriously increase the risk of crashes after half-an-hour, study finds
Even if feeling fully rested, the gentle vibrations can send people off
After half-an-hour the drowsiness affects concentration and alertness
Research was conducted on a simulated highway, other road types are unclear
Motor-vehicle crashes cause two million emergency-room visits a year in the US
Road-traffic accidents cause 0.5% of all fatalities in the UK; higher in teenagers
More @ Car vibrations make drivers drowsy in just 15 minutes, study finds | Daily Mail Online