Upgrading the infrastructure of ports and roads was a high priority for the Dutch, with the goal of modernising the economy, pumping wages into local areas, facilitating commerce, and speeding up military movements. By 1950, Dutch engineers had built and upgraded a road network with 12,000 km of asphalted surface, 41,000 km of metalled road area and 16,000 km of gravel surfaces. In addition the Dutch built of railways, bridges, irrigation systems covering 1.4 million hectares (5,400 sq mi) of rice fields, several harbours, and 140 public drinking water systems. These Dutch constructed public works became the economic base of the colonial state; after independence, they became the basis of the Indonesian infrastructure.