How does an interstate spur differ from a loop?

An interstate spur is defined as a connector that links with a primary interstate route at only one end, allowing drivers to access specific areas or cities without the need for a full loop. This type of route provides a direct path to destinations that might not be directly accessible from the main interstate highways.

In contrast, a loop would normally connect back to the primary route at both ends, essentially encircling an area and providing access from multiple directions. The spurs, on the other hand, serve a more focused function, leading to areas such as urban centers or points of interest without necessarily completing a circuit. This distinction is crucial in understanding the structure and purpose of different road types in the interstate highway system.