The Riyadh Metro work is expected to start in two months as the tunnel boring machine (TBM) parts from Germany have arrived, a report said.

The assembling of the TBM will take two months, the Arab News report said quoting a source. A 30-m-deep manhole with a diameter of 10 m or more has already been dug at the King Abdulaziz Road.

Work on the tunnel will start from the bottom of the manhole.

The project is believed to be the biggest of its kind in the world. About 40 per cent of the metro will be underground and half will use viaducts in what is the biggest infrastructure project in Riyadh’s history. The network will have a capacity of about three million passengers a day.

Three foreign consortiums are building the metro, with France’s Alstom, Canada’s Bombardier and Germany’s Siemens among the major participants.