Final answer:
An odd-numbered Interstate sign indicates a route that travels north to south, part of a system where odd numbers are used for longitudinal routes and even numbers for latitudinal routes.
Step-by-step explanation:
An odd-numbered Interstate sign using a single or double digit number indicates a route that travels north to south. In the United States, highways that fall within the Interstate Highway System follow a specific numbering scheme to provide navigational aids to travelers. These odd-numbered interstates are generally understood to be the major longitudinal (north-south) routes, with numbers increasing from west to east.
Meanwhile, even-numbered interstates are designed to be major latitudinal (east-west) routes, with numbers increasing from south to north. It's a helpful system because it gives drivers an immediate hint about the general direction of the highway. For instance, Interstate 95 (I-95) is an odd-numbered highway that runs along the East Coast of the United States from Florida to Maine, indicating a major north-south route.