On 28 May 2009, the first five stations, namely: Marymount, Bishan, Lorong Chuan, Serangoon and Bartley, of the 33.3km Circle Line (CCL) were added into the present SMRT railway system, enhancing convenience and connectivity for the nation. The remaining 24 stations is targeted to open from 2010 onwards.

The first mass rapid transit system came into operations in Singapore in 1987 and since then, the SMRT system had been further developed to serve more areas of Singapore.

This set of four commemorative circular stamps presents a miniature exhibition of the Circle Line system - the Circle Line system map against the Singapore map, a new Circle Line station in the underground system, the new three car Circle Line train, and the new Circle Line Operation Control Centre situated in Kim Chuan Depot - the world's largest underground depot for trains.