Posted speed limits tell you what the maximum speed is on that specific road. That is the speed that you are legally able to drive on the road.
remember that the posted speeds are intended only for the most ideal conditions
Yes, just follow posted speed limits.
about 45 hours
Parts of the German Autobahn do not have posted speed limits.
For safety.
They can if they have their lights and sirens going and have a valid reason to do so.
Roads are built for safety and speed limits are determined by the conditions of the road on which they are posted.
The four major speed laws typically refer to the laws that regulate speed limits on roadways. These include statutory speed limits set by laws, prima facie speed limits that allow flexibility based on conditions, fixed or regulatory speed limits posted on signs, and basic speed laws that require drivers to always operate at a safe speed regardless of posted limits.
The distance is ~475 miles. Allow 8 or 9 hours for the trip if running at posted speed limits.
75 mph
Most interstate highways were designed for the posted speed limits on those interstates.