GA review (see here for what the criteria are, and here for what they are not)
It is reasonably well written.
a (prose, spelling, and grammar): Handful of minor/incidental errors corrected while reviewing. Well written overall. b (MoS for lead, layout, word choice, fiction, and lists): Very well done.
a (references): A number of citations are to hard copy-only editions of The Straits Times, but I am more than comfortable assuming good faith on the part of the nominator (who presumably has access to such copies in Singapore; if these are second-hand citations derived from another source, such as a book, this should be further indicated). On a side note, wherever possible, the citations should include authors names, even for news articles. There are some citations to hard copy-only articles in The Straits Times that lack page numbers as well, which is not ideal. In the grand scheme of things, this is not a huge issue (but definitely something to consider should the article be further developed towards FA status). b (citations to reliable sources): The only issue to speak of is the use of Google Maps (see WP:RSP for the consensus on GMaps) as a citation when describing the general shape of the route. Perhaps just cite a geographically accurate map from another source, such as a transit authority, or even just a more geographically accurate map already on Wikimedia? c (OR): d (copyvio and plagiarism): No issues found with copyvio detector
It is broad in its coverage.
a (major aspects): The article covers in appropriate depth the history, construction, geography, funding, operation, future, and other related aspects of the line. b (focused):
@WhinyTheYounger the Land Transport Authority (Singapore's transit authority) doesn't have official maps published on the geographic route of the MRT lines. I previously cited OpenStreetMap, but changed to Google Maps, cos that was done for other articles like Victoria Line or MAX Red Line. ZKang123 (talk) 02:47, 11 January 2022 (UTC)[reply]