Construction on the $22.5bn Riyadh Metro project has started with digging work at five places in the city.

Expected to be completed over the next four years, the Riyadh Metro project includes construction of a 176.7km-long six-line automated metro network in the city and aims to enhance travel experience in the capital.

Work that is currently underway covers for the metro station at King Khaled International Airport, Al-Olaya Station, its control centre and railway maintenance station, reports arabnews.com.

Spread over an area of 28,000m², Al-Olaya Station will have potential to serve 400,000 daily passengers.

"Spread over an area of 28,000m², Al-Olaya Station will have potential to serve 400,000 daily passengers."

Located at the fifth terminal, the airport station will have three stations linked to King Abdullah Financial Center.

In line with construction of the metro network, the three contracts were awarded to Fast consortium, Arriyadh New Mobility Group (ANM) and Bechtel-led BACS consortium by Arriyadh Development Authority in July 2013.

Spanish construction group FCC-led Fast consortium will be responsible for construction of three lines spanning 73km, under a $7.82bn contract.

Fast consortium comprises Alstom; Samsung C&T; Strukton, Freyssinet, Typsa, and Setec.

Alstom will supply a fleet of 69 metropolis trains, along with communications based train control (CBTC), Hesop energy recovery system, and Appitrack tracklaying system, as part of its $1.6bn share in the contract.

ANM will construct the 40.7km Red Line from Madinah Road to Prince Saad bin Abdul Rahman Road, under a $5.21bnn contract, while BACS consortium will construct the 39km Blue Line from Olaya Street to Batha Street and Al-Hayer Road, and the 25km Green Line along King Abdullah Road.

Ansaldo STS will be responsible for automatic train control, CBTC and power supplies, which are valued at around $680m.