Spain's road network is facing up to an "unprecedented state of deterioration", according to a study published by the National Road Association (AEC).

The study, entitled "Needs for investment in conservation," says the state of Spain's roads is "deficient," and in many cases close to being classified as "very deficient", adding that they are in the worst condition since studies of this kind were begun in 1985.

The AEC calculates around 6.2 billion euros (8.6 million U.S. dollars) needs to be spent on repairing damaged road surfaces, signs, markings and crash barriers.

The Spain's road authorities said 94 percent of the amount should be invested on resurfacing, while around 330,000 road signs need to be replaced and 52,000 kilometers of road markings need to be repainted.

The metal crash barriers which run alongside many roads have also deteriorated since the last AEC study in 2011, although they are still considered to be in an "acceptable" condition. Lighting on Spain's highways needs improvement given that AEC consider 82 percent of that to be "inadequate."

According to the AEC, Spain's poor road conditions lead to several negative consequences, among which are a decline in the safety and comfort of road travel, increased maintenance costs for motor vehicles, higher levels of emissions and a fall in competitiveness with other countries in the region.

AEC President Juan Francisco Lazcano blamed the falling standards of Spanish roads on cost-cutting which he warned was a false economy given that "one euro not invested in time, means 5 euros need to be spent in three years and 25 euros after five years."

Highlighting the importance of road travel in Spain, AEC General Director Jacobo Diaz Pineda said "75 percent of the transport of merchandise and 90 percent of travel are carried out by road. We have no other option other than to invest in them," he said.