Final answer:
The slowest legal speed on an interstate highway is typically 45 to 55 mph in good conditions unless otherwise posted, but drivers should always adjust their speed according to road conditions.
Step-by-step explanation:
The slowest speed at which you may legally travel on an interstate highway in good weather, also known as the minimum speed limit, varies by location and is typically posted on signs. If such signs are not available, it is assumed that a driver should not impede traffic, and laws generally stipulate that driving more than 10-15 miles per hour below the speed limit could be considered impediment. In many states, the minimum speed on an interstate highway is around 45 to 55 miles per hour unless otherwise posted.
It is essential to obey these posted minimum speed limits or risk receiving a ticket for impeding the flow of traffic. Always remember that the minimum speed is there for safety, allowing traffic to flow smoothly and predictably. However, always adjust your speed according to road conditions and never travel faster than is safe for the conditions present.