For many trips, the interstate highways are the most efficient way to travel by automobile between two points. Being limited access highways, interstates do not have traffic lights except on rare occasions. They typically have speed limits of 55 miles per hour or more. And they are well maintained and have the latest safety features.
The number that is assigned to an interstate highway has a specific meaning in identifying its purpose:
Even numbered one- and two-digit interstates under 100 transverse the country west to east. Higher numbers are further north and lower numbers are further south. Those ending in 0 are typically longer, transversing nearly the entire country.
Odd numbered one- and two- digit interstates under 100 transverse the country north to south. Higher numbers are further east and lower numbers are further west. Those ending in 5 are typically longer, transversing nearly the entire country.
Like most other roads, all interstate highways have speed limits. The limits, which are controlled and enforced by the respective states where they are located, can vary, depending on the laws of that state, the volume of traffic, and other factors. Typical speed limits range from 55-75 miles per hour, though there are exceptions both above and below this.