The California Department of Transportation and Los Angeles County Metropolitan Transportation Authority will carry out a $1bn project to upgrade the Sunset/405 bridge in San Diego, US.

Work includes widening the 405 freeway, the reconstruction and replacement of bridges and building a ten-mile carpool lane.

The bridges at Sunset, Skirball Center Drive and Mulholland Drive will be replaced to accommodate the new lane and increasing capacity.

Work will also involve realignment of 27 on and off ramps and the widening of 13 existing underpasses and structures while building 18 miles of retaining and sound walls.

Other upgrade works include the widening of the Sunset bridge to 120ft and increasing its lanes from six to eight and equipping it to withstand earthquakes.

The contractor, Kiewit Corporation, is expected to complete the construction of the entire bridge by 2013.

The move is intended to improve traffic flow in the US city of Los Angeles, according to