The Land Transport Authority (LTA) is studying a plan to link the Central Business District, new Marina Bay Downtown and the future southern waterfront district by an underground road network.

If the project gets approved, it will free up surface space and improve living conditions of highly urbanised areas - as seen in other cities such as Brussels, Stockholm, Madrid, Paris, Hamburg and Boston.

Singapore's plan to build an underground road network dates back to 1980s, where it was conceived to accommodate a growing population. In 1996, the plan was revisited when LTA thought of a 30-kilometre subterranean road, consisting of two to four-lane roads beneath the city centre.

The idea was brought up again recently, this time under the 2013 Land Transport Masterplan, although it has been given a new name - Singapore Underground Road System (Surs) and will now be more extensive than before.

Experts on the matter said that going underground is inevitable.

Head of the urban transport management programme at SIM University said that with more development headed for the downtown, building underground roads is the next best option. He added that elevated bridges are seen as a less suitable solution for transport solution in the city as they damages the visual appeal and poses noise pollution.