The highway system in Puerto Rico is composed of approximately of roads in Puerto Rico, maintained by the Puerto Rico Department of Transportation and Public Works (Spanish: Departmento de Transportación y Obras Públicas) or DTOP. The highway system in Puerto Rico is divided into four networks: primary, urban primary, secondary or inter-municipal, and tertiary or local (Spanish: red primaria, red primaria urbana, red secundaria o intermunicipal, and red terciaria o local). Highways may change between networks and retain their same numbers. Highway markers Puerto Rico roads are classified according to the network they belong to. There are four types: primary, urban primary, secondary, and tertiary. In this regard, a primary road is one which is part of the primary network, an urban primary road is part of the urban primary network, etc. Generally, the same highway may change between networks, but the highway will continue to have the same number. For example, PR-1, connecting Ponce and San Juan, is signed as urban primary inside the Ponce city limits, then it is signed as secondary in Ponce's rural barrio Capitanejo, and then it is again signed as urban primary on its entry into the town of Santa Isabel. Primary roads are numbered 1 through 99, secondary roads are numbered 100 to 299, and tertiary roads are numbered 300 to 9999. In 2009, primary routes comprise about 14% of the total Commonwealth system mileage, secondary about 30%, and tertiary (municipal) about 56% of the total mileage. Less common markers At least two other markers can be observed in Puerto Rico roads today (2019). The first is the older style road marker which, above the route number, also had the outline of the main island of Puerto Rico with the words Puerto Rico on the outline as shown here. Until 1999, all non-tolled numbered highways in Puerto Rico had the same route marker, a square with a white-on-black half-circle with the route number in the bottom two thirds and a map of Puerto Rico with the words Puerto Rico written inside in the top third. A second road marker, used on the road through El Yunque National Forest, is the brown-colored upside-down trapezoidal marker with the road number on the top two-thirds of the sign and the words Bosque Nacional (national forest) on the bottom one-third, as shown. Roadway maintenance All Puerto Rico Highway System roads, regardless of the classification used, are maintained