sleeping in a car is never advised, on the side of a road or otherwise - if driving a long distance, drivers should always seek a proper, safe locations to rest, prepared ahead of time by plotting the stops along the route in advance of departing.

to avoid any potential issues with local laws, drivers should learn the basic traffic rules and road signs before embarking on a trip and always respect them while driving - though it is not uncommon for local drivers to disobey traffic laws, it is not a good idea seeing as it can lead to getting pulled over by police or causing an accident. 

in addition to respecting traffic signals, be sure to respect other drivers on the road as well - never argue with other drivers or exhibit any sort of road rage, and refrain from using the horn, and try to keep a defensive, non-agressive driving attitude and always pay attention to vehicles in the near vicinity.