At privatisation in 1995, services were operated by the Cardiff Railway Company, which traded as Valley Lines. This was subsumed by the new Wales & Borders franchise in 2001, which was subsequently awarded to Arriva in December 2003 and operates as Arriva Trains Wales. The December 2005 timetable introduced a further increase in services to 4 trains per hour 18 hours a day, and even a Sunday service for the first time (further improved in June 2006 to offer the same 4 trains per hour service from 11am to 4pm). In December 2005, Arriva employed a single car Class 153 to "shuttle" along the Butetown Line, upgrading from the 2 car Class 143 'Pacers' used for the service. Since then, the service frequency has been increased even more - there are now 5 trains per hour on the line every day of the week, which equates to one train every 12 minutes.
In July 2006 the service was due to be provided by a 1950s British Rail Class 121 "Bubble car" DMU. The unit finally entered service in 17 August 2006, only to be withdrawn for repairs two days later. The unit then re-entered service on 14 September 2006.
Below is the passenger volume from the year beginning April 2002 to the year beginning April 2010. Comparing the two years, Cardiff Queen Street's usage has increased by 30% whilst Cardiff Bay has increased 323%.
The annual passenger usage is based on sales of tickets in stated financial years from Office of Rail Regulation statistics. The statistics are for passengers arriving and departing from each station and cover twelve month periods that start in April. Please note that methodology may vary year on year.
On 16 July 2012 plans to electrify the line were announced by the Government as part of a £9.4bn package of investment of the railways in England and Wales.
The announcement was made as an extension of the electrification of the South Wales Main Line from Cardiff to Swansea and the electrification of the south Wales Valley Lines at a total cost of £350 million. The investment will require new trains and should result in reduced journeys times and a cheaper to maintain network. It is thought to start between 2014 and 2019.