Highways in Puerto Rico

The system of highways in Puerto Rico is made up of about of roads. It is managed by Puerto Rico's Department of Transportation and Public Works.
The roads in Puerto Rico are divided into four types:
A highway may contain several types of roads, but the highway will continue to have the same route number. Primary roads have numbers 1 to 99. Secondary roads are numbered 100 to 299. Municipal (tertiary) roads are numbered 300 to 9999.
Interstates.
There are three Interstate Highways in Puerto Rico. Together, they total . As with Interstate Highways in Alaska and Hawaii, these routes do not connect to the rest of the United States' Interstate Highway System. However, they still get money from the U.S. government.
These Interstate Highways run along tollways and roads that are not grade-separated, which means drivers must use a specially made group of ramps to get to the road. There are no signs for these Interstate Highways. They are signed as Puerto Rico routes.
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. 
The three Interstate Highways in Puerto Rico are: