The West Midlands is, let’s be honest, not a great place for walking. Birmingham’s fine city centre is throttled by massive ring roads, which the council spent much of the 20th century putting in and, thus far, much of the 21st century trying to take out. Beyond that, you’ll find a landscape of multi-lane highways, with central reservations wide enough for entire streets. In what other city would you encounter so many “islands” that turn out, on closer inspection, to be roundabouts?

It’s not a great place for public transport, either. Its rail network looks all right on a map, but local services are forced to compete with intercity routes for tracks and platform space, while the West Midlands Metro consists of a single tram line, from Birmingham to Wolverhampton, which has managed one piddling extension in 21 years. That leaves locals dependent on buses or, more often, the private cars that commuters opt for because their bus keeps getting stuck in traffic.

Compared with continental or American mayoralties that come with real statutory or fiscal powers, the mayor of the West Midlands is weak

But now, a possible saviour for weary Brummie commuters has appeared on the horizon. Andy Street, the former boss of John Lewis, has been the Tory mayor of the West Midlands since 2017, although you wouldn’t necessarily know it from his chosen campaign colour (green, rather than blue). On Tuesday, he unveiled a tube-style map of what the conurbation’s transport network could look like by 2040, provided it re-elects him next May.

The map shows an entire tram network, its lines, named mostly for local heroes such as Mary Lee Woods and Benjamin Zephaniah, stretching to every corner of the region. Besides that, you’ll find an overground, expanded through reopened freight lines and with 21 extra stations; a system of automated pods connecting the University of Warwick to the rail network; a people mover linking the airport to the National Exhibition Centre and HS2; and Coventry buried beneath mysterious blue spaghetti known only as “the Godiva line”.

More bafflingly, it also shows HS2 itself. If that seems an odd thing to include on a metro map – the tube map doesn’t note that trains to Birmingham visit Watford Junction – then that’s because this map isn’t really intended to show the future Midlands transport network at all. It’s intended, rather, to re-elect Andy Street.

Look closely, and there’s another subtle hint that this is more campaign tool than serious plan: the price tag. That £15bn is a lot of money, of course, but it’s surely not a coincidence that it’s also the figure generally attached, with ever-decreasing accuracy, to London’s Crossrail. The capital is spending this on one line, runs the subliminal message: look how much more you’d get for your money in the Midlands.

Fair point. But it’s still a lot of money, and it’s not money the mayor of the West Midlands actually has. It amounts to £750m a year for the next 20 years, which Street says will come from a combination of developer contributions, borrowing against future ticket sales and bungs from central government. Each of those is plausible, but none is guaranteed – and, really, if you were running for local government at this point in history, would you make your pitch dependent on Whitehall largesse?

There’s another problem: it’s not clear that Street can actually do any of this. Politically, transport investment is tricky: the benefits take years to show up, but the traffic-snarling disruption happens immediately. What’s more, delivering these plans will require the mayor to work not just with central government, but with Network Rail, as well as the seven council leaders – both Labour and Tory – who still hold political sway on the ground. If any of these groups don’t like a proposal, there’s little Street can do. Metro mayors can advocate, persuade or cajole. But compared with continental or American mayoralties that come with real statutory or fiscal powers, the mayor of the West Midlands is weak. That said, one of the powers metro mayors do have is that of the bully pulpit. By banging the drum for their region, they can attract investment; by getting those power brokers in a room, they can hammer out a plan. Just by talking about plans like this, Street could guarantee them a momentum that will create a political cost for any council leader or minister who tries to get in their way.

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One of the first mistakes Boris Johnson made as London mayor was to abandon a bunch of Livingstone-era infrastructure plans on the grounds they didn’t have funding. (This seems quite funny, when you consider everything that came later.) Most of those schemes wouldn’t have happened; but by scrapping them all, Johnson guaranteed they would never see the light of day. By laying into Street’s masterplan, Labour may make a similar mistake, attacking minutiae without putting forward an alternative vision. The plan had been out in the world for two days before Labour even named Liam Byrne as its candidate.

Most of Street’s big plans will never come to fruition either, and they’re obviously more electoral politics than practical policy. But by thinking big he might make it very slightly more likely that, one day, the West Midlands could be a great place not to have a car after all.

• Jonn Elledge is a freelance journalist and former assistant editor at the New Statesman