London Midland, owner of the West Midlands franchise, began operating a single PPM50 (Class 999) unit on the Stourbridge line on Sundays in 2006, with a Class 153 diesel multiple unit (DMU) providing a weekday service. In June 2009, the Class 153 was replaced by two PPM60 units, classified as Class 139 (with one as spare), providing a 10-minute frequency in both directions. Although the capacity of the unit (60 passengers) is less than the DMU, overall capacity is increased due to the greater frequency, up from 4 to 6 trains per hour. The trains were transferred to West Midlands Trains, operating under the West Midlands Railway brand, when the West Midlands franchise was refreshed in 2017.