Puerto Rico Highway 10 (PR-10) is a major highway in Puerto Rico. The primary state road connects the city of Ponce in the south coast to Arecibo in the north; it is also the shortest route between the two cities.

Construction on the modern PR-10, a new 68.26-kilometer (42.41 mi) highway, began in 1974. The highway is being built parallel to the old PR-10; that road is now signed PR-123. Most of the new PR-10 is now complete, with an approximately 10-kilometer (6.2 mi) stretch still remaining to be finished. In its current state it is a freeway only in the completed portions, which consists of over three-fourths of the highway.

In May 2010, Autoridad de Carreteras estimated the road would be completed in 2015, at a cost of $500 million. Upon completion, the highway is expected to become one of the two major roads on the island that cross the Cordillera Central mountain range. The first section of the road was inaugurated in the year 2000. After "more than 40 years" since the project was initiated, as of 22 January 2017, 10 kilometers (6.2 mi) remained to be completed.

PR-10 runs generally north-south over the scenic mountains of the Cordillera Central with magnificent views of the surrounding mountain tops. After its initial completion, the road was described as "(being) of first class construction throughout, and present(ing) a panorama of magnificent scenery, rivaling the views of any of the famed roads of Europe." When completed, the reconstructed highway will significantly reduce travel time. Due to the rugged terrain, several sections of the new highway required the construction of bridges.

PR-10 has its southern terminus at PR-5506, near PR-1, at the entrance to Mercedita International Airport. The first four miles runs northwesterly, bypassing the City of Ponce to the north.. The road crosses barrio Sabanetas, intersecting PR-52, leading to Mayagüez and San Juan. The road also crosses barrio Machuelo Abajo, and an interchange with PR-14, which goes to downtown Ponce and Coamo. In barrio Machuelo Arriba, there is an interchange with PR-505 which leads to downtown Ponce and barrio San Patricio. Further west it meets PR-503 in barrio Portugués, which leads south to downtown Ponce, north to barrio San Patricio, and to barrio Consejo in southern Jayuya. This interchange also connects to PR-504, which leads to downtown Ponce and to the northern areas of barrio Portugués. The road then enters barrio Portugués Urbano where it intersects the northern terminus of PR-9, which leads to PR-2 in Ponce's barrio Canas.

At this point PR-10 turns sharply north and heads into the mountains of barrio Tibes. Halfway through Tibes it intersects PR-503. It runs briefly through barrio San Patricio before entering barrio Guaraguao. As it enters barrio Guaraguao, the road intersects with PR-515, which leads to PR-123, the old road between Ponce and Arecibo. Continuing on its northerly course, PR-10 then enters the municipality of Adjuntas via Adjuntas' barrio Portugués, where the headwaters of Ponce's Río Portugués is located. As the road goes from Adjuntas' barrio Portugués to barrio Saltillo, it intersects with Puerto Rico's Panoramic Route, PR-143, which leads to downtown Adjuntas and Barranquitas. As it continues north bypassing the town of Adjuntas, PR-10 intersects with PR-521 leading to downtown Adjuntas and to PR-143. The newer freeway alignment briefly continues north but comes to an abrupt end at a temporary terminus, requiring motorists to detour on the narrower PR-5516. After a short run south on PR-5516, a road signed PR-5518 continues the detour to PR-123, old PR-10,. The detour route continues north until it meets the new limited access PR-10.

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  PR-10 north in Ponce
• 
  PR-10, near intersection with PR-503, Barrio Tibes, Ponce, Puerto Rico, looking south

PR-123/PR-10 is a curvy road that leads to Utuado, the next town before the new PR-10's terminus in Arecibo. At this point the road traverses some of the tallest peaks of the Cordillera Central. The older road has views of the nearby mountains, but probably not as good as the views from the new PR-10,. This is due to removing trees along the new road for shoulders, thus making for a clearer view.

PR-10 continues north, intersecting PR-135, which leads west to Lake Guayo, located between Adjuntas and Lares. It continues north for approximately 15 miles before reaching another section of new PR-10, just prior to the town of Utuado. In this stretch, construction of the realigned PR-10 is visible, alternating between the left and right sides of PR-123, as it carves through the mountains. The headwaters of Río Grande de Arecibo is near here, and the river -is visible mostly to the east of PR-123. PR-123 intersects with PR-524, which leads west to Jayuya. About one-half mile south of the town of Utuado, PR-123 intersects with PR-603, which connects to another section of realigned PR-10. This section7 bypasses downtown Utuado and heads towards Arecibo.

PR-10 runs alongside Río Grande de Arecibo for several miles. The road intersects with PR-111 which leads west to the town of Lares, in the lower Central Karst Zone, and east to downtown Utuado and on to Caonillas Lake west of Utuado. The roads continues north where it intersects the old road to Arecibo, PR-123. Further north the road also intersects PR-621 which leads to PR-146 and Dos Bocas Lake, a major source of hydroelectricity. Traversing the Central Karst Zone, PR-10 follows a course parallel to Rio Grande de Arecibo. A connecting road, PR-6626 accesses PR-626, which leads to various rural Arecibo barrios. Continuing north, PR-10 descends from the mountains and enters Puerto Rico's northern coastal valleys. It intersects again with PR-123 acerca de San Pedro. Shortly after, the road becomes a divided highway. Further north, the road intersects PR-651 connecting to Hatillo, and PR-652, which accesses the 6barrios along the southern edge of the City of Arecibo, and leads to the former Arecibo Observatory. There is an interchange with PR-22, the main limited access highway on Puerto Rico's northern coast. A little over a mile later, PR-10 terminates at an intersection with PR-2.

The history of PR-10 is closely linked to PR-123 (the old Ponce-to-Adjuntas Road) which predates it.

PR-123 dates to the late 19th century when it was built under the colonial government of Spain to connect the coffee-growing town of Adjuntas to the port city of Ponce as a farm-to-market road.

When the PR-10 road started construction in the mid-1970s, the then Ponce-Arecibo Road, which used to be signed PR-10, was resigned PR-123 and the new road was signed PR-10. Today, PR-10 signs refer to the new road, whereas PR-123 signs refer to the old road. The old road is roughly parallel to the new PR-10. The exception to this is in the area between the towns of Adjuntas and Utuado, where construction of PR-10 is not yet complete and traffic is detoured to use the PR-123. In that area PR-10 signs identify the old road. Prior to 1974, the full length of the old road was, in fact, signed PR-10. This route signing can still be seen in some old street maps of the city of Ponce. PR-10 is an alternate route to PR-123.

Navigating the old Ponce-Arecibo road was very tedious as the road was engineered to run from mountainside to mountainside, following the contours of the mountains, and along the natural definitions of the course of rivers, to reach its destination. Driving was rather hazardous, especially for trucks.

One of the reasons to build a new road was the expected use by large trucks which the old road could not accommodate. Also, as traffic on the old road increased in the 1950s and 1960s, that road started to show its limits. To ameliorate the situation, in 1974 the Puerto Rico Department of Transportation and Public Works started planning for the construction this road to connect the cities of Ponce and Arecibo. While one of the main reasons to build the new PR-10 was to facilitate the movement of trucks in the mineral exploitation of the area, such exploitation met with considerable opposition from environmental advocates and today the road is being built to promote other types of socio-economic developments, such as those associated with the Port of the Americas.

PR-10 was inaugurated in the year 2000.

The new Puerto Rico Highway 10 is being built in three segments and, as of November 2010, only the middle segment remained to be built. The first segment, the road from Utuado to Arecibo was built at a cost of $120 million; the second segment, the road from Ponce to Adjuntas, was built at a cost of $80 million.

The remaining segment, from Adjuntas to Utuado, is partly complete. Due to the complexities of road-building in the remaining segment, this last segment is being built in nine phases. The first phase, consisting of 1.24 km of roadway, was completed at a cost of $7.9 million and opened to the public on 21 August 2009. Phases 2 and 3 were already also under construction at the time that the beginning of phase 4 was announced on 25 August 2010. Phase 4 will cost of $8.7 million. At that juncture, phase 5 was being readied for bidding. The last four phases were under engineering design in August 2010. The total cost of these last five phases (phases 5 through 9) is projected to be $179 million. During a 2013 presentation by the Puerto Rico DTOP, the last three Utuado-to-Adjuntas phases that were at that point in the design phase ("etapa de diseño"), and known as phases II, III, and IV (synonymous with former phases 7, 8, and 9), would cost $31.8M, $31.3M, and 34.5M, respectively, to build for a total cost-to-build of $97.6 million.

The new road runs mostly parallel to PR-123, and for the area that is still under construction, motorists must use a stretch of PR-123 before reaching PR-10 again. The incomplete stretch will link Adjuntas to the mountain town of Utuado. It takes about half hour travel on PR-123 to reach the new PR-10 road, and about one hour and 20 minutes to travel the full length of the road from Ponce to Arecibo. Before the building of the new PR-10 highway, just the stretch from Utuado to Arecibo used to take one hour to travel; it now takes 15 minutes.

On 8 November 2010, large rocks fell on a section of the new PR-10 in barrio Tibes leading to a 24-hour closure of the highway. It was the second time that heavy rains had caused rocks to fall onto the highway in a period of a few months. Meanwhile, northbound traffic was detoured to PR-515 and southbound traffic was detoured to PR-123, the old PR10-signed road. As a result, the Puerto Rico DTOP is assessing whether the area would be a candidate for the installation of metal nets that would minimize the possibility of further erosion.

The building of the new PR-10 was an issue of contention based on environmental reasons related to the effect on the virgin Cordillera Central. When a group of American corporations attempted to lease land from the Government of Puerto Rico to exploit nickel, copper and cobalt mines, a grassroots effort by Puerto Rican townspeople had the government turn away from the idea. The plan had its roots in a so-called Plan 2020, the result of a study by a group of U.S. consultants eyeing economic regeneration for Puerto Rico at the expense of the environment.

The frequent rain and high humidity as well as the mountainous terrain of the area traversed by PR-10 make for a road building challenge for road engineers who have come to the use of recycled ground vehicular rubber tires as an innovative solution. The government calls PR-10 "Puerto Rico's first green road" for its use of recycled car tires to build the surface of the road.

No plans have been disclosed to close the old PR-123 after the new PR-10 construction project is complete, and PR-123 will likely serve mostly as a local route. Today, the old highway is signed as PR-123 in those stretches of the road where the newer PR-10 parallels it. As new stretches of the PR-10 road are completed and opened to traffic, the corresponding stretch of the old PR-10 road is being signed PR-123.

The new highway was anticipated to be completed by 2015 at a cost of $500 million, however remains incomplete at the present moment. When the new PR-10 highway is completed, travel time between Ponce and Arecibo will be significantly reduced. The new PR-10 provides a second safe route to cross the island from north to south, in addition to PR-52. Except for a 1.65-kilometer (1.03 mi) stretch of road between km 13.45 and km 15.10, where the road is only two lanes wide, the road is either a three- or four-lane highway. The road is listed as part of the National Highway System.

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  Southern terminus of PR-10 at PR-5506 intersection in Ponce
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  PR-10 north at PR-9 interchange in Ponce
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  PR-22 east approaching PR-10 interchange in Arecibo
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  Northern terminus of PR-10 at PR-2 junction in Arecibo

Municipality	Location	km	mi	Destinations	Notes
Ponce	Vayas–Sabanetas line	0.0	0.0	PR-5506 west – Santa Isabel	At-grade intersection; southern terminus of PR-10 and counterclockwise terminus of PR-5506; PR-1 access is via PR-5506
				Aeropuerto Mercedita (Avenida Aeropuerto), Central Mercedita (Calle La Esperanza)
	Sabanetas	1.9– 2.0	1.2– 1.2	PR-52 – Juana Díaz, San Juan, Ponce Centro, Mayagüez	Cloverleaf interchange; PR-52 (unsigned PRI-1) exits 98A and 98B
	Machuelo Abajo–Machuelo Arriba line	4.2– 4.3	2.6– 2.7	PR-14 – Ponce Centro, Juana Díaz	Diamond interchange; PR-139 and PR-505 access is via PR-10 north entrance
	Machuelo Arriba	5.4	3.4	To PR-139 / PR-505 / PR-Avenida Emilio Fagot (unsigned) – Ponce Centro, Machuelo	At-grade intersection; Avenida Glenview access is via Avenida Emilio Fagot north
	Portugués	7.0	4.3	PR-503 – Tibes	Partial cloverleaf interchange; access to PR-504, Ponce Centro and the Tibes Indigenous Ceremonial Center
		8.2– 8.3	5.1– 5.2	PR-9 west – Ponce Oeste	Trumpet interchange; northern end of freeway and southern end of expressway; northern terminus of PR-9
	Tibes	8.8	5.5	PR-503 – Tibes, Machuelo	Access to the Tibes Indigenous Ceremonial Center and Sector La Vaquería
		13.2	8.2	Pastillo Tibes (Camino La Zarza)	To PR-588
		14.9	9.3	PR-503 – La Jácana, Aguacate, Burene	Carretera David Medina Feliciano
	San Patricio	18.5	11.5	PR-515 – Guaraguao	Eastern terminus of PR-515
Adjuntas	Saltillo	24.3– 24.4	15.1– 15.2	PR-143 (Ruta Panorámica Luis Muñoz Marín) – Jayuya, Barranquitas	Access to PR-123 and Bosque del Pueblo
	Vegas Abajo	28.5– 28.6	17.7– 17.8	PR-521 – Vegas Arriba	Adjuntas Centro access is via PR-521 west; the Garzas Water Filtration Plant is located at km 29.3
	Juan González	29.7– 29.8	18.5– 18.5	PR-5516 east – Adjuntas Centro	Northern terminus of PR-5516
		30.5	19.0	PR-123 to PR-135	Temporary northern terminus of southern segment; all northbound traffic must exit; access to Adjuntas Centro, Utuado and Lares
Temporary gap in PR-10
Utuado	Arenas	38.2	23.7	PR-123 – Utuado, Adjuntas	Temporary southern terminus of northern segment; all southbound traffic must exit
	Salto Arriba	41.6	25.8	To PR-123 / PR-6103	Access to the former PR-603 and the University of Puerto Rico at Utuado
	Salto Abajo	42.7	26.5	PR-111 – Utuado, Lares, Caguana	Access to the Caguana Ceremonial Ball Courts Site and Hacienda Horizonte
		43.8	27.2	San Martín, Salto Abajo	To PR-123
	Río Abajo	48.4– 48.5	30.1– 30.1	PR-6613	Northern terminus of PR-6613
		51.0	31.7	PR-6612 to PR-621 – Río Abajo	Southern terminus of PR-6612; access to Río Abajo State Forest
Arecibo	Río Arriba	53.3	33.1	PR-621 – Florida, Ciales, Jobos	Access to Dos Bocas Lake
	Hato Viejo	60.5	37.6	PR-6626 to PR-626 – Calichoza, Esperanza	Eastern terminus of PR-6626
		62.0	38.5	PR-123 – Hato Viejo, Carreras	Partial cloverleaf interchange; northern terminus of PR-123 and southern terminus of PR-6609; no access to PR-6609 from southbound
	Tanamá	64.2	39.9	PR-636 – Charco Hondo, La Planta, Macelo	Eastern terminus of PR-636
		65.4	40.6	PR-651 – Tanamá, Central Los Caños	Clockwise terminus of PR-651
		66.6	41.4	PR-6109	Northern terminus of PR-6109 (former PR-6609)
		67.1	41.7	PR-652 – Higuillar, Dominguito	Eastern terminus of PR-652; access to the Arecibo Observatory
		68.3	42.4	PR-22 – Bayamón, San Juan, Manatí, Aguadilla, Mayagüez, Hatillo	Cloverleaf interchange; PR-22 (unsigned PRI-2) exits 75A and 75B
		69.0	42.9	Calle Ingeniero Manuel T. Guillán
	Arecibo barrio-pueblo	70.1	43.6	PR-2 – Mayagüez, San Juan	Northern terminus of PR-10
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Incomplete access       Route transition       Unopened

• List of highways in Ponce, Puerto Rico
• Anillo de Circunvalación de Ponce

• PR-10 as it crosses Barrio Pellejas, in the municipality of Adjuntas
• A three-lane section of PR-10 in the municipality of Adjuntas
• PR-10 changing from a 2 to a 3-land road in barrio Tibes in the municipality of Ponce