Rapid, my poor commuting arse...

Dublin (ok, fair enough) Area (just the eastern part of the area though, the other areas can shag off) Rapid (the cheek!) Transport (I suppose, in the same way as cattle trucks or barges full of nuclear waste are forms of transport). 
D.A.R.T. 
Dublin Area Rapid Transport
D.A.R.T. 
Rhymes with FART. Smells like old ones too, embedded in the vintage green upholstery. 

Rapid... Rapid... my arse. 

The genius who came up with the acronym deserves his head on a pike. Mounted on the ergomically-challenged front of a vintage Dart (there are no other types). And paraded around the Dublin area (eastern part only) at 28 km/h (top speed of the DART). 
That will teach him about needlessly raising the customers' expectations.