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 69
Texas continues to actively pursue completing its portion of I-69 by upgrading existing US and state highways along the I-69 corridor to interstate standards. Several portions of the 15 SIUs in Texas are currently being worked on, with active construction in progress on US-59 from SH-99 to Kendleton (SIU 20), and on US-77 between Robstown and Kingsville (SIU 22). Four mainline SIUs outside of Texas are under construction; SIU 3 in Indiana (using $700 million from the 2006 Major Moves deal), SIU 7 and SIU 9 in Tennessee; also a small part of SIU 13 in Arkansas (Monticello Bypass). Portions of these SIUs are open to traffic. Most of the remaining parts of the mainline are in the environmental impact statement (EIS) stages; FHWA has signed records of decision approving the final EIS for SIUs 11, 12, and 13.