Maximum speed limits are posted on most of the roadways. These speed limits are not just recommended, but enforced by the highway patrol. These are set for the type of roads and traffic in each area. All speed limits are based on ideal driving conditions. Remember, breaking the posted speed limit and driving faster than is safe for current conditions is dangerous and illegal.
In most states (e.g.,California, Massachusetts, Michigan, Oregon, Utah) a Basic or Fundamental Speed Law is enforced. According to the law you may not drive faster than is reasonably safe for road conditions, regardless of the posted speed limit. Thus, it is not always lawful to drive as fast as the posted speed limit. You must be able to control the speed of your vehicle at all times no matter what the weather condition or traffic situation is on the road.