List of Interstate Highways
There are 70 primary Interstate Highways in the Interstate Highway System, a network of controlled-access freeways in the United States. They are assigned one- or two-digit route numbers, whereas their associated "auxiliary" Interstate Highways receive three-digit route numbers. Typically, odd-numbered Interstates run south-north, with lower numbers in the west and higher numbers in the east; even-numbered Interstates run west-east, with lower numbers in the south and higher numbers in the north. Highways whose route numbers are divisible by "5" usually represent major coast-to-coast or border-to-border routes (ex. I-10 travels from Santa Monica, California, to Jacksonville, Florida, traveling from the Pacific to Atlantic oceans). Additionally, auxiliary highways have their numbering system where a different number prefixes the number of its parent highway.
Interstate 89
Interstate 89 was unique due to one instance of its signage. Between (Vermont) Exits 9 & 10, a sign showing the distance to the next control cities in each direction was completely in metric. While there are many instances of signs being in both miles and kilometers, this was the only case of solely metric in the entire Interstate System. Both signs were replaced in 2010 and show distances in miles only. (Interstate 19 in Arizona used to be the other "only signed in metric" interstate in the U.S., but has been changed over in recent years as the last 2 km have been changed.) Speed limit signs have always been posted in mph.
After Exit 11 in Richmond, I-89 leaves the Green Mountains to enter the Champlain Valley, and a notable shift in the landscape is visible. Here, just outside Burlington, the highway turns northward once again. Also, at this turn is where the only "official" auxiliary highway starts, Interstate 189. A second highway, Interstate 289, was proposed as a beltway through Burlington's northeastern suburbs in the 1980s; amidst controversy, the highway has only been partially completed as Vermont Route 289, a super two roadway. It has yet to directly meet its parent.