What exactly is the South Wales metro? The bullet train to the bay, a revolutionary rail service, or – according to Pontypridd AM Mick Antoniw – not a metro system at all, but rather the Loch Ness monster?

Having been described as all three in the space of two days, it is safe to say the proposed metro system is a hot topic in the politics of the Welsh Assembly. But in the rest of the UK, where transport headlines are dominated by HS2 and Crossrail, relatively little has been said of this expansive infrastructure project.

The first phase of the scheme, servicing what the Welsh Government refer to as the "Cardiff Capital Region’, is due to complete in the next five years. This, simply put, is the eastern section of South Wales – from Bridgend in the west to Monmouthshire in the east.

The region is estimated to have a population of 1.5m, and growing. For scale, that’s about half of the Welsh population.

The first phase of construction is currently underway. This is predominantly focused the heavy rail backbone of the service, as well as new stations in Newport’s Pye Corner and Ebbw Vale Town.

Antoniw’s evocation of the Loch Ness monster – a comparison I’m sad not to see more in transport circles – laments several rejected improvements during later phases of the line. His argument was that “nobody knows whether it actually exists or not”.

This rhetorical flourish also speaks to another concern: whether the system will be truly cohesive. After the completion of Phase II, on which work is due in 2023, the result will not be a ‘metro’ in the familiar sense of an urban rail system: instead, bus, tram and train lines will connect and rely on one another.

So will it feel like a single system at all?

The proposed map. Click to expand. Image: Welsh Government.

The Welsh government is determined to make clear that it will: a major aspect of the marketing to date has centred on the “seamlessly connected” system. It’s promised that ticketing will be integrated. It’s also formed a new body, Transport for Wales, to join up the formerly atomised bus and train services across the area. The incorporation and improvement of previously built rail services into the body is, in many ways, the same as TfL’s acquisition of the London Overground.

A rarity in British metro systems, however, is the inclusion of a Bus Rapid Transit (BRT) system, which will be used as the cross-Newport service and across the valleys. The Welsh Government insists this is for where demand for services is too low to make capital-intensive light rail investment worthwhile.

BRT systems do not involve buses as much of Britain is used to them, but buses with prioritised road space and fewer stops, like a permanent rail replacement service. Notably used at scale in Brazil and Indonesia, there are forms of BRT across Europe in dedicated busways.

Oooh, integrated ticketing. Image: Welsh government.

Even if Transport for Wales can integrate rail, tram systems and BRT effectively into a single system effectively, which is far from certain, one pertinent question remains – will it benefit residents?

The increased capacity for the railways in Cardiff, as well as much lower commuting times for those living in the metropolitan area, should ease housing and road demand across the region.

But a concern for those in the poorer regions of the South Wales metro area is that – with easier links to Cardiff – areas in the valleys may become increasingly expensive to live in, and dominated by commuters to the capital. At present, according to property moguls Zoopla , two out of the ten cheapest areas to buy a house in the UK are in the South Wales valleys – Blaenau Gwent and Merthyr Tydfil.

In a BBC interview on the metro system, Dr Mark Lang of the Federation of Small Business Wales warned that the routes could weaken communities, insisting that the economic benefits of infrastructure investment “must be felt not only at Cardiff but in communities across south east Wales that are served by the Metro network”.

Nevertheless, Welsh Government analysis shows that a number of stations in the valleys, on lines leading to Aberdare, Merthyr Tydfil and Rhymney, all suffer congestion as the rail system currently stands.

The new metro should ease this congestion. Ken Skates, the Welsh Cabinet Secretary for Economy & Transport, has also pledged to flatten fares for half the stations in the valleys, to make transport cheaper for residents.

The results of Transport for Wales’ work will be clear soon enough. It is likely to be a great asset to the major metropolitan hubs of South Wales, particularly if it is as seamlessly connected as the Welsh Government are insisting.

Time will tell, however, whether the economic benefits, too, will be integrated.