Speaking of my Dad, he drives one of those REALLY big diesel powered vehicles, and was recently telling me that NY has a law of some fashion that makes it illegal for diesel vehicles or maybe more specifically semi-trucks to idle for a length of time (I forget the amount of time). Being that he travels to NY on a weekly basis he had to invest a chunk of change in a generator (I believe it runs on gas) that will run all the accessories of his truck including the heat/air to keep it temperate for sleeping. In the long run it's all a good thing... in many ways for him... but this seemed to actually have some legitimacy ... after all he will let it idle for HOURS at a time, particularly in cold weather so the diesel fuel doesn't gel.