Scheduled to open in three phases in 2019, 2020 and 2021, the 30km north-south line will run entirely underground from Woodlands North to the Central Business District and Marina Bay.

It will largely parallel the existing North-South Line, providing an additional 60 per cent capacity to help relieve crowding along the corridor.

The Thomson Line’s 22 stations will include six interchanges connecting with all five existing metro lines, and daily ridership is predicted to reach 400,000.

Land Transport Authority has now awarded 22 of the 25 major civil contracts for the line, with the remaining three to be awarded by the end of this year.

Ground-freezing construction techniques are to be used on the metro network for the first time, to prevent water seepage during tunnelling at Marina Bay where the Thomson, North-South and Circle line tunnels will intersect.

Technically, ground-freezing is to freeze the ground to turn the ground water into ice, to form ice wall, so that to facilitate the construction to solidify the ground and to facilitate the construction of the tunnel. This will prevent water from seeping in and weakening the soil.

"The Thomson Line marks yet another milestone towards realising our Land Transport Master Plan’s vision to double the length of our rail network", said Minister for Transport Lui Tuck Yew at the ground-breaking ceremony. "When this is achieved by 2030, our MRT system would be comparable in network density to New York and London. By then too, eight in 10 households will be within a 10 min. walk from a train station."

In the long term, the Thomson Line will be linked to Johor Bahru in Malaysia via a cross-border rapid transit link from Woodlands North station.