Puerto Rico Highway 172 is a main highway that connects Caguas, Puerto Rico

Caguas, Puerto Rico

Caguas , founded in 1775, is a city and municipality of Puerto Rico located in the Central Mountain Range of Puerto Rico, south of San Juan and Trujillo Alto, west of Gurabo and San Lorenzo, east of Aguas Buenas, Cidra, and Cayey....

 at PR-1

Puerto Rico Highway 1

Puerto Rico Highway 1 connects the city of Ponce to San Juan. Leaving Ponce, the road follows somewhat parallel along the southern coast of the island and, at Salinas, it turns north to cut through the Cordillera Central in its approach to San Juan....

 to downtown Cidra, Puerto Rico

Cidra, Puerto Rico

Cidra is a municipality of Puerto Rico located in the central region of the island, north of Cayey; south of Comerío and Aguas Buenas; east of Aibonito and Barranquitas; and west of Caguas. Cidra is spread over 12 wards and Cidra Pueblo...

 and continues its way to its end at Puerto Rico Road 156 in Comerio

Comerio

Comerio is a comune in the Province of Varese in the Italian region Lombardy, located about 50 km northwest of Milan and about 8 km west of Varese...

, Puerto Rico. It is a two-lane per direction road from Caguas to its border point to Cidra and rural all the way to Comerío.

Dangerous Highway

Puerto Rico Highway 172 has about 4 kilometers going uphill. One side of the road is extremely close to the blasted mountain (See Blasting), meaning that landslides would fall in the right lane of the direction close to it; the other side is near a precipice, with barriers that are not safe. The two directions are not divided, and cars can easily collide front-to-front. Several people have died in this highway, including cars which have been collided by heavy-weight trucks that come so fast downhill their brakes malfunction or don't have to time to stop. The most recent death occurred July 9, 2008. Only one emergency ramp has been built to provide safety in the down part of the mountain.

Rural Road in Cidra

Similar to other highways in Puerto Rico which become rural after entering another town from the town of origin, PR-172 becomes rural and enters downtown Cidra before continuing to its end at Puerto Rico Road 156 in Comerío

Comerio

Comerio is a comune in the Province of Varese in the Italian region Lombardy, located about 50 km northwest of Milan and about 8 km west of Varese...

. It is mainly flat, and there are no precipices found in the rest of the highway.