Marie-Louise ten Horn-van Nispen and Wim Ravesteijn, "The road to an empire: Organisation and technology of road construction in the Dutch East Indies, 1800-1940," Journal of Transport History (2009) 10#1 pp 40-57 In addition, the Dutch built 7500 kilometers 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.