Fun Fact Friday: Asymmetrical Half-Height Platform Screen Doors

Did you notice that the first and last half-height platform screen doors are different?

The half-height platform screen doors (or PSD for short) were installed onto elevated MRT stations between August 2009 and June 2012. All of the 24 doors along the platform might look the same, but the first and last doors are a wee bit different – one side of the door is smaller than the other.

This design is to prevent the door nearest to the headwall and tailwall to protrude out excessively from the panel when the door is opened. If the doors were of the same width, it would prevent staff from accessing the staff-only areas of the platform through the train cab door when the train doors are opened.


This is an issue that is only present for half-height platform screen doors as the drive mechanism is located at the bottom panel next to each door. The drive mechanism needs to be in contact with a portion of the door for it to control the door movement, and this portion of the door will protrude into the access area if the doors are of the same width. The drive mechanism for full height platform screen doors at underground stations are located above the doors and hence, there is no need for the asymmetrical first/last platform doors.

We covered the retrofitting of the Half-Height Platform Screen Doors at elevated stations a month ago in this article, click on to read more!

Fun Fact Friday: Retrofitted Platform Barriers at Elevated Stations


Matthew Ng

An avid train enthusiast since 2009, he designs graphics and infographics to promote the little known facts about Singapore's train network.