In case you weren't aware (who are we kidding, of course you are), SMRT trains on the North-South and East-West Line (NSEWL) have been running at slower speeds since 2013 due to the sleeper replacement project.
What the project set out to do was basically upgrade Singapore's oldest rail line. So the Land Transport Authority (LTA) and SMRT embarked on replacing the 188,000 wooden sleepers (those slabs of planks in between rails) with modern pre-stressed concrete ones.