Viaduct over Indigenous Forests at Langeni

The seven span viaduct, total length 245m, is located on the section of road where it descends from the Ncembu plateau to the Langeni Sawmill, traversing steep mountainous terrain with some deeply incised valleys. This mountain pass section which covers a distance of 8 km at a gradient of 11% is the steepest surfaced pass in South Africa and was completed in 2008. A real challenge for the designers was to find a route down the mountainside which minimised the impact of the road on the indigenous forest, accommodated the problematic geotechnical conditions, and provided a safe geometric alignment for the road user. On one particular horseshoe bend this meant reducing the design speed to 45km/hr.