Arriva is a major train operator in the UK with over 14 years’ experience in providing passenger rail services. ARRIVA UK TRAINS. Arriva is a major train operator in the UK with over 14 years’ experience in providing passenger rail services. Arriva runs ftheirrail franchises and two rail contracts that cover 22 per cent of the entire network, as well as the UK’s first modern light rail service. Arriva operates the Northern franchise, the second largest rail franchise in the UK, and runs regional and commuter services across the region. Arriva is committed to improving journeys with nearly £500 million being spent on 98 brand new trains and 281 air-conditioned carriages, refurbished trains, the complete retirement of Pacer trains, better stations and more services.