The recommendation follows a year-long investigation into ways to reduce congestion on the M4 motorway caused by the volume of traffic at peak times. The commission, headed by Lord Burns, found this was a symptom of the wider problem of a lack of alternatives along the route. 

While bus and rail services do run along the corridor, these are often slower, more expensive and do not accommodate the type of journey’s regularly being made, the report found.  

The commission says the preferred network approach puts a focus on integration, allowing for flexible journeys while reflecting the diversity of trips that people want to make. “When the different parts work together, its value can be greater than the sum of its parts,” the report says. 

To construct the network, the commission has recommended an infrastructure package that will: 

  • create a new south east Wales ‘rail backbone’ by significantly increasing the capacity and flexibility of the SWML 
  • transform access to the rail network by increasing the number of stations between Cardiff and the river Severn from three to nine 
  • create new rapid bus and commuter cycle corridors across Cardiff and Newport, connecting to the rail backbone and Cardiff City Council’s public transport proposals, and 
  • establish a ‘hub and spoke’ network of bus and cycle corridors within Newport.  

In order to integrate the network, the commission has recommended a network policies package that will: 

  • integrate ticketing across all services, organised through a cross-city zonal fare system 
  • coordinate bus and rail timetables at key points of interchange 
  • deliver hassle-free interchange between rail and bus services, and 
  • adopt a single brand and consistent standards for all stations and services. 

Services on the existing four-track mainline will be segregated, with stopping services using the northern two tracks while express services would use the two southern two tracks. Head of secretariat, Mr Peter McDonald,  told a media briefing on November 26 that the stopping services would be an extension of existing services from further afield as opposed to a shuttle service between Cardiff Central and the Severn Tunnel Junction.  

The programme will cost between £590m and £840m, including £130-180m for rail upgrades and reconfigurations, £140-190m for consequential rail improvements, and £120-170m for new stations along the SWML. 

In order to go ahead, the programme would need the support of the British government, which has alternatively proposed the development of a relief road to reduce congestion on the M4. Unlike road infrastructure, the funding and management of the rail network in Wales is not devolved to the Welsh government. But Lord Burns says that he is still confident there is the support to develop the project.  

“I have no reason to believe that this cannot be done as a joint project, regardless of one's position with regards to the relief road,” he says. “They’re not alternatives. There is a strong case for this project regardless of what happens with the relief road. This is something for the long-term. It’s something that the region is going to need if it is to really reach the best of its potential.  

While smaller improvements such as the active travel routes and introduction of improved bus services could be implemented within the next five years, the commission says the rail backbone and new stations will take several years to deliver.