Final answer:
Odd-numbered Interstate routes signify north-south highways, with numbers increasing from west to east as part of the systematic numbering of the Interstate highway system.
Step-by-step explanation:
An odd-numbered Interstate highway using a single or double digit number typically indicates that the route is a north-south highway. The numbering system for the Interstate system was designed with a specific pattern in mind: odd numbers are used for north-south routes and increase from west to east, while even numbers are used for east-west routes and increase from south to north. This system helps with navigation and indicates the general direction of the highway. As more and more cars came into existence, the need for an organized interstate highway system became essential, leading to the establishment of this numbering scheme.