There are a number of laws on the books here in the states about drivers (especially commercial (ie truck, bus) drivers) being required to sleep a certain # of hours a day, in order to help prevent fatigue-caused accidents. Unfortunately, there isn't at the moment any real method of determining whether or not said drivers are actually following the rules. IIRC the drivers are supposed to keep logs of how many hours on the road/miles driven and what hours they are at 'rest', but logs can be falsified, and often are. It seems the Europeans have found a way to make it easier for the police to check on such information, plus make it harder to falsify data.
I was a USAF security police officer assigned for three years to Hahn AB in Germany (now a commercial airfield, the military part of the base being closed down years ago) and can tell you that even 25 years ago, European law regarding driving a motor vehicle were a lot more stringent than the US rules, even today. For example, even back then they had laws requiring you to wear seat belts - and if you weren't wearing a seat belt and were involved in an accident - even if the accident wasn't your fault - your insurance company did not have to pay you anything for losses, hospital time, etc. (Reasoning was that if you had had a seat belt on, you wouldn't have been thrown around inside your vehicle, could have kept better control of your vehicle, etc.) Americans, who are used to a much 'looser hand' as far as laws of the road, tend to freak out a little when confronted with the differences in traffic laws, especially when pulled over by German police for something that wouldn't even be an infraction here stateside... been there, done that, got the patches on my Levi jacket to prove it...