Transport for Wales used its Class 142 "Pacer" trains on the commuter lines around Cardiff, Barry and Penarth known as the Valley lines. All of its Class 142 "Pacer" fleet wore the turquoise and cream house colours of Arriva Trains Wales. The Class 142 units were also primarily used on South Wales Valley line routes and routes through the Vale of Glamorgan. On Valley and Vale of Glamorgan services, Class 142s were often coupled together with Class 143 or Class 150 units to cope with demand on the busy Valley Lines network. The Class 142s received minor refurbishments with retrimmed seats in new moquette, plus the installation of ceiling-mounted CCTV cameras.