The US Department of Transportation’s Federal Highway Administration (FHWA) has announced the opening of the $1bn I-405 northbound carpool lane in Los Angeles, California.

The project is expected to increase capacity and safety between the I-10 and US-101 roads, while easing traffic congestion on a key motorway in the Los Angeles area.

A central part of the I-405 project, the new carpool lane also includes new sound walls and the reconstruction of three bridges across the road.

"We need US Congress to pass a long-term transportation bill so that we can continue investing in significant projects."

US Transportation Secretary Anthony Foxx said that widening one of the nation’s busiest motorways is good news for the entire Los Angeles region.

"We need US Congress to pass a long-term transportation bill so that we can continue investing in significant projects such as this one to reduce congestion, improve safety and create ladders of opportunity for thousands," Foxx said.

The I-405 freeway links the San Fernando Valley to Los Angeles’ westside via the Sepulveda Pass.

With the new construction, the carpool lane will now extend from Orange County to the US-101 freeway, becoming the longest continuous carpool lane in the US.

The new ten-mile long lane reduces travel time and completes the final remaining gap in the entire I-405 carpool lane network between Orange County and north Los Angeles County.