Those road number signs are the route numbers assigned to a particular road. They're part of the Route Numbering System (RNS) that the Department of Public Works and Highways (DPWH) developed in 2014 in order to simplify and rationalize navigation along national roads classified as primary which directly connects major cities of at least around 100,000 people; and secondary or other roads which complement with the national arterial roads.
Those roads provide access to main population and production centers of the country by directly connecting cities, major ports, airports and ferry terminals, and tourist service centers.
Here are some of the route numbers that the DPWH officially created to the main roads in the Philippines:
| Island | Road Section | Route Number |
|---|---|---|
| Luzon | Laoag - Gataran |
1
|
| Luzon | Aparri - Gataran | 101 |
| Luzon | Laoag - San Fernando - Agoo - Rosario - Urdaneta - Tarlac - Angeles - San Fernando - Manila | 2 |
| Luzon | Gataran - Tuguegarao - San Jose - Cabanatuan - Guiguinto | 1 |
| Luzon | Bontoc - Baguio | 204 |
| Luzon | Baguio - Rosario | 54 |
| Luzon | Bugallon - Tarlac | 55 |
| Luzon | Bugallon - Alaminos - Olongapo | 306 |
| Luzon | Olongapo - San Fernando | 3 |
| Luzon | San Fernando - Gapan | 3 |
| Luzon | Tagudin - Cervantes - Sabangan | 205 |
| Luzon | Manila - Santo Tomas - Tiaong - Lucena - Calauag | 1 |
| Luzon | Kawit - Naic | 402 |
| Luzon | Santa Rosa - Tagaytay | 420 |
| Luzon | Santo Tomas - Lipa | 4 |
| Luzon | Calauag - Tagkawayan - Sipocot | 68 |
| Luzon | Santa Elena - Daet - Sipocot | 1 |
| Luzon | Pili - Tigaon - Legazpi | 630 |
| Luzon | Sipocot - Naga - Legazpi - Matnog | 1 |
| Samay | Catarman - Laoang - Taft | 670 |
| Samay | Wright - Taft | 674 |
| Panay | Nabas - Ivisan | 503 |
| Panay | Nabas - San Jose - Iloilo | 501 |
| Panay | Roxas - Ivisan - Iloilo | 5 |
| Panay | Roxas - Pilar - Zarraga | 505 |
| Cebu | Bogo - Cebu City - Santander | 8 |
| Bohol | Trinidad - Clarin - Tagbilaran - Loay | 850 |
| Bohol | Trinidad - Carmen - Loay | 852 |
| Bohol | Trinidad - Ubay - Loay | 850 |
| Mindanao | Dapitan - Oroquieta - Ozamis | 79 |
| Mindanao | Iligan - Malabang | 77 |
| Mindanao | Surigao - Davao - Digos | 1 |
| Mindanao | Cotabato - General Santos | 1 |
| Mindanao | Cotabato - General Santos | 1 |
| Mindanao | Iligan - Ampayon | 9 |
| Mindanao | Bugo - Maramag | 10 |
| Mindanao | Maramag - Kabacan | 943 |
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