Puerto Rico Highway 66 (PR-66) is a main tollway which parallels Puerto Rico Highway 3 going from the city of Carolina, Puerto Rico via a 3 loops cloverleaf interchange with PR-26 and PR-3, a major exit in the form of a Trumpet interchange in Canóvanas, Puerto Rico and ending in the municipality of Río Grande, Puerto Rico with an intersection of PR-3. It is only 19.5 kilometres (12.1 mi) long and has very few exits, which work mainly to minimize traffic in the congested Carolina area of PR-3.

Puerto Rico Highway 3 (PR-3) at nearly 100 miles long, is the second-longest highway on Puerto Rico. It connects the San Juan neighborhood of Río Piedras to downtown Salinas indirectly around the eastern coast of the island. Highway 3 ranges from a three lane urban avenue in San Juan to a one lane rural road past Fajardo. While other roads connect San Juan, it runs the coastline of Puerto Rico east of San Juan, beginning in Río Piedras near Santurce and goes to Fajardo where it goes south paralleling the coastline to Humacao and Maunabo. It goes up to a mountain-scenic route and goes west to Salinas, where it meets PR-1.