Sosrobahu is a road construction technique which allows long stretches of flyovers to be constructed above existing major roads with minimum disruption to traffic. The technique was designed and invented by Indonesian engineer Tjokorda Raka Sukawati and involves the construction of the horizontal supports for the highway beside the existing road, which are then lifted and turned 90 degrees before being placed on the top of the vertical supports to form the flyover pylons. This technique is of considerable value in increasing road mileage in large cities where there is limited right-of-way for new roads and the closure of existing roads throughout the flyover's construction using normal techniques would impose significant economic costs. The term sosrobahu was derived from Old Javanese which means "thousand shoulders". Background By the 1980s, Jakarta was experiencing increased traffic congestion, and flyovers were seen as one solution to the improving transport infrastructure. One construction company operating at that time was PT Hutama Karya, which was granted a contract to build a highway above Jalan A. Yani, an extremely important stretch of highway where it was vital that the road would continue to be open to traffic throughout the period of construction. In addition to this challenge, PT Hutama Karya were also granted a contract to build a flyover between Cawang and Tanjung Priok in 1987. The most difficult issue was the requirement to support the road with a row of concrete pylons (pier shafts) apart, on top of which would sit the wide road supports. The vertical pier shafts were to be sextagonal in shape with a diameter of , and were to sit in the central lane of the existing road. The erection of the pier shafts was not difficult; what caused problems were the poured concrete pier heads. With conventional construction techniques, the pier heads would be moved into place with the help of iron supports beneath the outspread pier heads, but the use of iron supports would necessitate the closure of the road below. Another option was to support the pier heads from above, but this increased the costs of the project. In response to these problems, Tjokorda had the idea of initially erecting the concrete pier shafts and then building the poured concrete pier heads in the centre lane, parallel to the existing roadway, and then raising and turning the pier heads 90 degrees into place. The only problem with this