Commuters travelling on the East-West Line (EWL) and North-South Line (NSL) will experience shorter operating hours over weekends and full closures on some Sundays next month at 19 stations.

The move will affect 17 stations from Tiong Bahru to Tuas Link on the EWL, and NSL's Bukit Batok and Bukit Gombak stations.

The shortened operating hours are expected to affect 20,000 to 30,000 people.

Train operator SMRT said on Tuesday that this is done to accelerate resignalling works and move the EWL onto the new signalling system by June next year, instead of the end of next year.

Compatibility issues between an old signalling system and a new one caused two MRT trains to collide on Nov 15. The changes are put in place to avoid the risk of a repeat incident. This also means that there will be no train service between Joo Koon station and Gul Circle on the EWL, as a way to keep the two signalling systems separate, until next June.

Here is what commuters need to know:

SHORTER OPERATING HOURS ON FRIDAYS, SATURDAYS AND SUNDAYS

When: From Dec 8 to 30, train services will end at 11pm on Fridays and Saturdays at 19 stations - from Tiong Bahru to Tuas Link on the EWL, and Bukit Batok and Bukit Gombak stations on the NSL.

When: From Dec 9 to 31, the first trains at those stations will also start later at 8am on Saturdays and Sundays. Alternative arrangements: Commuters can take parallel bus services - which run along the MRT network - outside affected MRT stations. They will be charged the same fare as if they have taken a train journey.

FULL-DAY CLOSURES ON TWO SUNDAYS

When: The 19 stations - from Tiong Bahru to Tuas Link on the EWL, and Bukit Batok and Bukit Gombak stations on the NSL - will be closed for the whole day on Dec 10 and Dec 17.

Alternative arrangements: Parallel shuttle bus services will be made available on the two Sundays. These buses will ply the same route as the MRT trains. The fares for these shuttle bus services will follow the rail fare structure.

FULL CLOSURE BETWEEN JOO KOON AND GUL CIRCLE UNTIL MID-2018

When: Train services have been suspended between Joo Koon and Gul Circle stations. This will continue until mid-2018.

Alternative arrangements: Commuters will have to alight at either stop and take a free shuttle bus to the other station in order to continue their journey. They will be charged the same fare, as if they have taken a train straight through.

REDUCED TRAIN SERVICES ALONG OTHER STRETCHES IN FIRST HALF OF 2018

When: Disruption to services will happen at other stations along the NSL and EWL in the first half of next year. More details, closer to the dates, will be revealed.

Alternative transport: Parallel shuttle bus services will run along those stretches as and when train services are affected.