It ran urban and inter-urban passenger services to all railway stations in Wales, including Cardiff Central, Cardiff Queen Street, Newport, Swansea, Wrexham General and Holyhead, as well as to certain stations in England such as Hereford, Shrewsbury, Chester, Crewe, Manchester Piccadilly and Birmingham New Street.

In March 2010, Arriva Trains Wales' application to reinstate a direct Aberystwyth to London Marylebone service was rejected by the Office of Rail Regulation due to concerns over its financial viability, as well as the potential severe revenue abstraction from other operators such as Wrexham & Shropshire.

In July 2012, the Department for Transport announced that the Cardiff Valley Lines would be electrified, although this ambition would not be substantiated during Arriva Train Wales' franchise period.

During the mid-2010s, as the franchise period was nearing its end, tenders were sought for its next operator; Arriva Trains Wales' publicly withdrew from the process in October 2017 despite having been shortlisted.

[5] In October 2002, a shortlist of Arriva, Connex/GB Railways, National Express and Serco-Abellio were invited to bid for the new franchise period.

At its height, ATW operated over a route length of 1691 km, with 253 diesel multiple unit (DMU) cars and 22 locomotive-hauled passenger carriages.

[17] The latest figures released by NR (Network Rail) rate punctuality (Public Performance Measure) at 96.1% for period 7 of the 2013/14 financial year.

Holyhead services ran every hour, to Shrewsbury via Chester and Wrexham General, then alternately to Birmingham International or Cardiff Central.

Request stations west of Llandudno Junction (Conwy, Penmaenmawr, Llanfairfechan, Llanfairpwll, Bodorgan, Ty Croes, Rhosneigr and Valley) were generally served by alternate trains.

The Conwy Valley Line were operated by a single train running between Llandudno and Blaenau Ffestiniog, with six return journeys a day.

Services were operated exclusively by Class 158 Express Sprinters, as they were the only units fitted with the necessary equipment for the ERTMS system used on the line.

[29][30] ATW operated an hourly long-distance service from Carmarthen to Manchester Piccadilly via Cardiff Central and the Welsh Marches Line.

[31][32] ATW also operated the Heart of Wales line between Shrewsbury and Swansea via Llandrindod, with four trains per day in each direction.

Special trains extending into South East Wales operated to Builth Road during the Royal Welsh Show annually in July.

Stations in the valleys north of Cardiff experienced strong passenger growth, as a result of which there was a new half-hourly service launched (Pontypridd-Treherbert, Abercynon-Aberdare, Abercynon-Merthyr Tydfil and in the future Bargoed to Rhymney).

Stations on the Treherbert and Rhymney branch lines were lengthened to accommodate six-car trains to cope with future growth demand for commuting into and out of the capital.

One year after opening, the line had carried 573,442 passengers, beating all targets set by the Welsh Assembly Government.

[35] Possible developments that never saw the light of day also included restoring the service between Ebbw Vale and Newport; before Arriva discontinued operations, the proposal awaited Network Rail and Welsh Government approval.

[40] Wrexham & Shropshire[41] and Grand Central[40] expressed an interest in operating the service, but the contract was awarded to Arriva Trains Wales.

[citation needed] It originally ran via Crewe but, in September 2012, the service was rerouted via Wrexham General, which required the train to change direction at Chester in addition to having its evening departure moved from 16:15.

[citation needed] In April 2015, ATW were highly criticised and issued an apology for their continual poor performance when dealing with the Judgement Day rugby matches at the Millennium Stadium.

A spokesman for the company said “I want to assure all customers that every single train in Wales was out [on Saturday].” He added that the event differed to international rugby events, because the majority of those travelling to the matches travelled from south and south west Wales, placing huge pressure on specific routes.

[45] Arriva Trains Wales used to operate services from Manchester Piccadilly, Pembroke Dock, Carmarthen and Swansea to London Waterloo, Brighton, Portsmouth Harbour, Plymouth and Penzance via Cardiff, Bristol and Westbury.

As a result of this our owning group would be unable to sustain additional and continuing losses and the WSMR service would cease to exist.

"[47][page needed] In March 2010, it was announced that the application has been rejected by the Office of Rail Regulation due to concerns about the financial viability of the service and the potentially high level of revenue abstraction caused to other operators.

During the mid-2010s, as Arriva Trains Wales' 15-year franchise period came towards its scheduled end date, the process to select a successor was started.

[64][65] In February 2018, rival firm Abellio also opted to withdraw, which was largely due to its partner company Carillion having effectively collapsed and entered liquidation one month earlier.