SINGAPORE - The replacement of rail junctions requires more time now than before because of higher service frequency and competing works that are going on after revenue service.

This is why train services along some parts of the East-West Line will end earlier on several days in April and May.

SMRT Trains deputy director of permanent way Kelvin Tan said at a briefing Friday morning (April 7) that the replacement of railway junctions - totalling 170 in the North-south, East-west line network - would all be done after revenue hours.

Typically, SMRT engineers would lock up the switching rail at a junction - the part which moves to allow trains to switch to another direction - for the day to finish the replacement work.

Trains at a terminal station would then have to turn around at another nearby junction - something which takes a bit more time.

But because trains are running at a higher frequency today than "four to five years ago", Mr Tan said locking up a junction would cause unacceptable delays to more commuters.

Mr Tan added that other projects in the network, such as resignalling and third rail replacement, meant that there were shorter windows for the junction replacement works.

He said engineering hours - the time after the last train pulls into the depot and the first train starts running in the morning - have "always been insufficient".

"But because of all the other activities today, things have become even tighter," he said.

Because of this, SMRT is ending service between Lakeside and Joo Koon, as well as between Tanah Merah and Changi Airport earlier at 11pm on April 14 and 21 (Lakeside-Joo Koon) and April 28 and May 5 (Tanah Merah-Changi Airport).

Shuttle buses will be provided at these stations instead.

Junction rails are replaced every three to five years, compared with 10 years or more for the rest of the tracks. This is because they are exposed to greater wear and tear.