The rail service, then known as the ‘Arrow’, began operating on May 16 1994, a date that also marked the reopening of Sallins, Hazelhatch and Clondalkin stations along with the opening of a new station at Cherry Orchard. The service was somewhat slow to develop as Heuston as a terminus had little employment in its vicinity. Kildare station layout, with just the up and down lines and a loop on the up side and an under bridge, just south of the station, were restrictive and hindered development of a bay platform.

In 2002, funds became available for an improvement on the Kildare route, and taking into account the level of passengers at each station and the fact that the many main line trains calling at Kildare gave that station a frequent and fast service to Heuston, it was deemed prudent to provide a bay platform on the down side at Newbridge with an associated crossover to allow trains exit the bay to the up line. This proved very successful; down commuter trains could clear in off the main line quickly and not unduly hindering expresses.
In the early 2000's a bay platform was installed at Newbridge which allowed trains to terminate at Newbridge and not fowl the main platforms at Kildare.

Thanks to the "Celtic Tiger" boom of the 1990's / 2000's demand for passenger services on the Kildare route increased and Iarnrod Eireann developed the Kildare Route Project (KRP) to address this. The KRP quadrupled between Sarsfield Road Bridge, Inchicore & Hazelhatch. The former down and up lines are the down fast and down slow respectively and two new lines were constructed to the north of these to provide the up slow and up fast lines. The quadruple section is 7¼ miles long from MP3 to MP10¼. A number of over-bridges were constructed and underbridges widened.
Cherry Orchard and Clondalkin Stations were closed and both were resited slightly west of their original location. Clondakin / Fonthill & Cherry Orchard / Parkwest both opened in July 2008. New Stations were constructed at Adamstown (opened in July 2007) and Kishogue . Kishogue Station, completed in 2009, has yet to open due to the economic recession and remains idle to this day.

The four track section opened in 2010.

In January 2013 the Kildare Line Commuter service was extended to Portlaoise with an hourly service operating throughout the day. Some additional peak hour short workings to/from Newbridge & Kildare remain.

When opened in 1994, the route used the brand new 2600 Class Railcars built by Tokyu Car Corporation. Since then all of Iarnrod Eireann's DMU Classes have operated the route at various times throughout the last 20 years. Since 2009 the service is in the capable hands of the 22000 Class Intercity DMU's which are maintained at Laois Traincare Depot, Portlaoise.

To celebrate the 20th anniversary of the Kildare Commuter rail service, this weekend (Saturday 17th May and Sunday 18th May) Iarnrod Eireann are offering free travel to children under 16 along the Kildare-Heuston commuter line (when accompanied by an adult).
Free car parking at Iarnród Éireann car parks on the route (Kildare, Newbridge, Sallins and Hazelhatch).
It's our way of saying thank you to all in the communities along the route, who have supported the service over the past 20 years, with almost 25 million journeys made on the route in that time.

In preparing this feature I would like to express my thanks to the following people for allowing use of photographs.
- Jane Cregan & Joanne Bisset of Iarnrod Eireann Corporate Communications.
- Brian Solomon http://briansolomon.com/trackingthelight
- Josefstadt.