What do even-numbered highways indicate in terms of direction?

Even-numbered highways indicate East/West routes. This convention is rooted in the numbering system established by the Federal-Aid Highway Act of 1956, which created the Interstate Highway System. In this system, the numbering of highways is designed to aid in navigation and orientation.

Even numbers represent highways oriented east and west, making it easier for drivers to know their general direction based on the number of the highway they are on. For example, the Interstate 80 runs horizontally across the country from New Jersey to California, demonstrating this east-west orientation.

Understanding this system is important for drivers as it allows them to quickly ascertain their direction of travel just by looking at the highway number. While odd-numbered highways indicate North/South routes, the structure of even-numbered highways being used for east-west travel helps maintain a logical grid system that is intuitive for navigation purposes.