SINGAPORE - Ongoing multi-year projects to expand the MRT network and upgrade existing lines are on track, the Land Transport Authority (LTA) said on Friday (Nov 20).

As early as in the middle of 2016, trains on the North-South Line (NSL) will be able to run at shorter intervals of 100 seconds, instead of 120 seconds.

The LTA said in its quarterly rail report that work on the new signalling system for the NSL stations and tracks are more than 96 per cent complete as of October 2015.

More than half of the 141 trains in the current North-South East West Line (NSEWL) fleet have also been retrofitted with the new system, and system tests started in October 2015.

The East-West Line (EWL) will similarly have its signalling system upgraded by 2018.

At the same, the power-supplying third-rail of the NSEWL is also being replaced progressively, and the timber sleepers on the EWL replaced with concrete ones.

The third-rail replacement is expected to be completed by March 2017, while the re-sleepering project, by the end of 2016.

The third stage of the Downtown Line - a 21-km, 16-station stretch linking Fort Canning to Expo - is also on track for a 2017 opening, LTA said.

Most of the underground reinforced concrete works for the stations are completed, and work on the above-ground structures, such as ventilation shafts and entrances, installation of the electrical and mechanical works, as well as the architectural works in the stations are on schedule.

Meanwhile, tunnelling works for the 43km Thomson-East Coast Line, that will open in stages from 2019, started in August 2015 and the construction of earth-retaining structures for most stations are in progress, LTA said.

Excavation works for Caldecott, Gardens by the Bay, Marina South and Woodlands stations have started, it added.

At the Marina Bay station, which will be the interchange with three MRT lines by 2021, construction and ground improvement works are ongoing to cater for the construction of TEL tunnels below the existing NSL and Circle Line ones.