The highway is called the Roberto Sánchez Vilella Expressway, which is also the name given to the much larger PR-2 freeway segment from Hormigueros to Ponce. The second phase of PR-66 from Canóvanas to Rio Grande was opened on October 1, 2012.
PR-66 is, in reality, an extension of older expressway PR-26, as both expressways are attached (that is, there is no need to take an exit to enter the other expressway, much like PR-18 and PR-52). PR-66 was assigned that number after U.S. Route 66 in the United States.
PR-66 is very close to the El Yunque National Forest and at the beginning caused problems between developers and environmental activists. Several actions of disobedience took place, including beams already installed being removed. The expressway was planned to be extended to Fajardo but due to the close presence of the forest reserve, it was accorded to be extended to Río Grande and connect to PR-3 which has several exits between that municipality and Fajardo, and it might be possible that PR-3 is converted into a complete freeway in that segment as it approaches PR-53.
The short expressway is very expensive in terms of toll fees and many people still go through PR-3 as a consequence. There are no plans to turn the toll down or lower the current fee of $1.50. This makes this small freeway the second most expensive tollway in the US (excluding bridges and tunnels), after the Dulles Greenway in Virginia in terms of its small length (about 30 cents per mile). This results beneficial in the effect that PR-66 has low traffic almost all the time, including rush hours. As of December 2011, the toll must be paid by pre-paid AutoExpreso.
Puerto Rico Highway 26, called the Román Baldorioty de Castro Expressway, is the main highway to the Luis Muñoz Marín International Airport and is connected to PR-66. It was converted to a freeway to minimize the traffic in PR-3 and PR-17, to grant better access to the Airport. Several exits exist to provide access to PR-187 (the main route to the Piñones area), PR-37 (Isla Verde) and PR-22 (José de Diego). The combined routes of PR-26 and PR-66 is about 25.8 miles (41.5 km) long.