How are major interstate routes designated?

Major interstate routes are designated by one-digit or two-digit numbers, which are assigned according to a specific numbering system. Generally, the numbers are based on the geographical layout of the country, with odd-numbered routes running north-south and even-numbered routes running east-west. For example, Interstate 95 (I-95) runs along the East Coast, while Interstate 10 (I-10) runs across the southern part of the country.

The two-digit numbering system helps drivers easily identify major highways and their significance, as lower numbers are typically associated with major east-west and north-south routes. This systematic approach to interstate numbers contributes to navigation and overall roadway efficiency.

In contrast, the other options, such as three-digit numbers, are used for auxiliary routes that branch off from the major interstates, while letters and symbols do not play a role in the official designation of major interstate routes. Having a clear understanding of the numbering system can significantly assist drivers in planning their travel routes and understanding the layout of the interstate highway system.