The society has developed several bases over time, with Whitehead joined by Sallins, then Mullingar, and also Inchicore and Connolly in Dublin.

Whitehead, near Belfast, has a long history as an excursion station, and the RPSI developed a working steam and engineering depot there.

[3] The museum contains five galleries and it is possible for visitors to see various heritage steam and diesel locomotives and observe work on railway carriage restoration.

[6] The site was eventually handed back to the local council and Irish Rail, in preparation for new housing development, with remaining carriages moved to other locations, including one to the new Maam Cross railway project.

Whithead still operates within the yard on train rides while maintenance.is still carried out on the mainline cariages and locos based here, ready for the future.

These locomotives are suitable for longer distance main line work, but are speed restricted if they need to run tender-first in the event they cannot be turned.

461, a 2-6-0 DSER 15 and 16 Class heavy goods locomotive, is the only Dublin and South Eastern Railway example that has been preserved.

[21] In the 2000s, with more rail stringent regulations, the RPSI was forced to acquire rakes of metal bodied carriages for mainline railtours.

[22] Whitehead has a collection of historic wagons, including a GNR brakevan named Ivan, restored by their award-winning Youth team, a Guinness van and NCC handcrane and a GSWR ballast hopper and an oil tanker from Irish Shell.

The main work of the society is in securing and maintaining steam rolling stock, with a view to running rail tours and Mulligan, in "One Hundred and Fifty Years of Irish Railways" noted that the RPSI did "sterling work" in the area of organising of such rail tours around the island, following the end of steam as a regular means of service provision on UTA and CIÉ lines.

[23] The RPSI has been able to assist in the provision of suitable rolling stock for train-related scenes in films made on the island of Ireland.

It is published annually[25] On 7 November 2014, an RPSI train chartered by Web Summit blocked a level crossing in Midleton for over 25 minutes.

The Civil Defense had to cool down the boiler with hoses while the crew were evacuated from the cab and a rescue diesel summoned from Dublin.