The $160 million Sentosa Gateway Tunnel, the construction of which was delayed for a year, could open as early as April.
The two-lane tunnel starts at the stretch between VivoCity and St James Power Station, and goes under Telok Blangah Road, before forking out into two single-lane roads - one to Lower Delta Road and the other to Keppel Road.
It will allow motorists leaving Sentosa to bypass the busy junction between Sentosa Gateway and Telok Blangah Road, as well as the one at Telok Blangah Road and Kampong Bahru Road.
The tunnel only goes one way.
The Land Transport Authority (LTA) had said previously that motorists who use the tunnel can halve their travel time.
Travel time on the surface level will improve by a quarter.
LTA said yesterday that it has completed the structural, electrical and mechanical works for the project and is now in the final stages of work, such as road surfacing.
The tunnel is then scheduled for testing works before it can be opened to the public "shortly thereafter", an LTA spokesman added.
Tests include running through procedures for vehicle recovery, in the event of a breakdown, for example.
The project was announced in 2008 to cope with the expected increase in traffic volume with the launch of Resorts World Sentosa in 2010, along with new residential and commercial developments on Sentosa.
Work started in 2010 and was targeted to finish at the end of 2015.
But the complexity of the construction forced the delay.
The road tunnel is located just 1.6m above the North East Line MRT tunnels and about a metre away from the foundations of the West Coast Highway Viaduct.
Extra care had to be taken to ensure that the surrounding structures were not affected by the tunnelling.
Dentist Justin Ang, 41, who lives on Sentosa, said: "Traffic out of Sentosa can be slow moving during the weekends.
"With the tunnel, I can bypass the traffic junctions and cut down on my travel time to Lower Delta Road."
Businessman Adrian Koh, 39, who shops at VivoCity, said: "When you exit the mall carpark and get onto Sentosa Gateway, it is usually quite congested.
"I have to wait for two to three traffic light cycles before I can clear the junction with Telok Blangah Road."
This article was first published on Jan 26, 2017.
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