Ever since been introduced in October 2006 the MKIV fleet has led a rather mundane life operateing between Dublin and Cork on the hourly Intercity Service with the odd working from Heuston to Portlaoise or Thurles on Commuter services. Planned Train Size in passenger service has always been 8 vehicles long until today. (There was one exception on the 27th September 2007 following a derailment in Cork Yard when a one way movement of a 6 car occured on the 1830 Cork - Heuston).
On Monday 6th December 2010 the spare set, consisting of a 6 car MKIV set (4007 + 4201 + 4408 + 4126 + 4139 + 4135) entered service in an effort to increase fleet availability for the Cork line and the ability to recover from delays during the inclement weather. Its first workings were the 0800 Heuston - Cork and 1130 Cork - Heuston.
The return working from Cork is pictured passing Clonkeen, near Portlaoise in freezing conditions.