Cholan Express (Chennai Egmore to Trichy) has RSA with Pandian Express (Chennai Egmore to Madurai) and Rockfort Express (Chennai Egmore to Trichy) with base at Madurai.
Cycle is like this
Pandian (MDU...
more... MS) - Cholan (MS TPJ) - Rockfort (TPJ MS) - Rockfort (MS TPJ) - Cholan (TPJ MS) - Pandian (MS MDU).
Composition is 9 SL, 5 3A, 3 2A, 1 1A, 3 UR, 2 EOG. 23 coach LHB rake.
With this RSA, GSN Yard in Chennai and the Trichy Yard save one space. (earlier Rockfort was a dedicated rake with base at Egmore, Cholan had RSA with Egmore Mangalore Express, base at Trichy).