Debate over rail or tram system for south Wales
6 August 2014 Last updated at 20:01 BST
Should the electrification of the railway line between the south Wales Valleys and Cardiff be scrapped in favour of a tram system?
One rail industry expert has told BBC Wales Today that trams would be cheaper and more effective.
Electrification is a key part of the metro project which, it is hoped, will improve transport links into the capital city by 2030.
Business correspondent Brian Meechan reports.