Final answer:
An interstate route sign with an even number suggests the road is an east-west highway, as per the numbering system of the U.S. interstate highway system.
Step-by-step explanation:
An interstate route sign ending in an even number typically indicates that the road is an east-west highway. This is part of a systematic numbering convention used for the interstate highway system in the United States. Route numbers ending in odd digits generally run north-south, while those ending in even digits run east-west, facilitating navigation and orientation. It's interesting to note that the lower numbered routes are usually found in the south and west, with numbers increasing as you move north and east.