changed, extended, or abandoned, leaving discrepancies in the system. In other cases, it may not be possible to use the proper number because the limited set of available numbers has been exhausted, causing a "non-standard" number to be used. Spur route A spur route's number usually has an odd number for its first digit. It is usually one of the following: It may serve another section of a city or metropolitan area not served by the main freeway (most often the central business district), terminating at a regular city street/avenue or at a substandard freeway, such as I-185 in Columbus, Georgia. It may represent the first portion of a contemplated extended freeway, one that downgrades to below Interstate standards with plans to upgrade it later on. An example is I-540 in Arkansas. It may connect two unrelated Interstate highways—as I-390 in New York State and I-355 in Illinois do. Note that states differ on their interpretation of the numbering convention in this case. In the I-390 example above, the route has both ends at Interstates, but not at the same Interstate on both ends, and is assigned an odd first digit. Another example is I-275 in Tennessee: it is a connector between I-40 and I-75 (a similar case of having both ends at Interstates but not at the same Interstate) and is assigned an even first digit. Examples include: I-110 in California links I-10 with the Port of Los Angeles. This freeway was built before Interstate Highways as the Harbor Freeway. Later, it was adopted into the Interstate Highway System. I-180 in North-Central Pennsylvania connects Williamsport and Lycoming County with I-80 in Milton, which does not actually enter Lycoming County. I-180 also serves as a connection to those traveling to New York and I-86 via U.S. Route 15 and the Future I-99 Corridor at its western terminus. I-190 in New York connects the cities of Niagara Falls and Buffalo with I-90. Sometimes, a three-digit Interstate Highway branches off from another three-digit Interstate Highway. These spurs do not connect directly with their parent highways, but are associated with them via the three-digit highways they do intersect with. Examples include: I-380 in Northern California is located at the San Francisco Bay Area. This highway begins at I-280, and it connects with US 101 and San Francisco International Airport. I-190 in Massachusetts branches off from I-290 near Worcester. I-795 in Baltimore County, Maryland