The Busan–Gimhae Light Rail Transit, a private investment project costing US$ 1,2 billion, connects the cities of Busan and Gimhae via light rail transit. This project is the first commercially qualified driverless light rail system in South Korea. The project is 23,2 km in length, consists of a steel box girder bridge 8,9 m in width and 15 m in height, and is the longest bridge structure in South Korea to date. The major structure consists of 21 stations and one depot. The route passes through an area of thick, soft ground deposits at the mouth of the Nakdong River. The deepest sedimentary layer is 85 m. To optimize the foundation design of the bridge structure, pile load tests were performed. Based on the results of these tests, it was determined that friction piles would be constructed rather than the more commonly used end-bearing piles. The 1,6 km section passing through the Nakdong River was constructed in the form of a 5 × 80 m steel box girder bridge, and the remaining section as a 2 × 50 m bridge. The total number of piers is 448. When the route passing through the center of the city was constructed, all processes were performed in a working area only 18 m in width, so as not to disrupt the flow of traffic. This project had a 5-year construction period, and was completed in April 2011. The light rail system was opened to public in September 2011, after test drives.