Interstates
Puerto Rico has 410 km (250 mi) of Interstate highways. There are three designated Interstate Highways in Puerto Rico. As with Interstate Highways in Alaska and Hawaii, these routes do not connect to the rest of the United States Interstate Highway System, but still receive funding in a similar fashion to the Interstates in the contiguous US.
As with Interstate routes in Alaska, Puerto Rico Interstate routes are unsigned. The designated routes of the three routes — officially PRI-1, PRI-2 and PRI-3 — run along various combinations of Puerto Rico routes. They do not follow the rules of even and odd numbers determining direction used in mainland United States. Per Section 103(c)(1)(B) (ii), Title 23, United States Code (23 U.S.C.) Puerto Rico is exempt from the design standards of Section 109(b).
Puerto Rico's interstate routes are not to be confused with Puerto Rico Routes PR-1, PR-2, and PR-3. These are other major highways in Puerto Rico.
Read more about this topic: List Of Highways In Puerto Rico