Today, Mayor Boris Johnson unveiled designs for a new generation of London Underground trains. Transport for London plans to build 250 of the new trains to increase capacity in some of the busiest parts of the network: they’ll be introduced first on the Piccadilly line, then later on the Bakerloo, Central and Waterloo & City.

And, at first glance, they are very shiny indeed. This video rendering shows the new trains in action, complete with lingering piano music and shadowy commuters:

From the outside, the new trains look satisfyingly futuristic – but the changes they’ll offer passengers aren’t actually that dramatic. Here’s what Londoners need to know.

1.They’ll be driverless. (Ish.)

The trains will have the capacity to run completely unaided and unstaffed, but TfL has said they’ll use onboard operators when they launch. The firm produced two designs, and one, it’s worth noting, retains the driver’s cab – not something the Docklands Light Railway, which is more committed in its driverless-ness, bothers with.

2. They’ll carry more people.

The trains will come equipped with “modernised” signal systems, and TfL says they’ll enable “faster, more frequent and reliable services with fewer delays”.

Overall, they estimate that the trains will generate at least a 25 per cent passenger capacity increase on each line:

According to TfL, the Piccadilly and Central lines will get 100 new trains apiece, with 40 on the Bakerloo and 10 for the Waterloo & City (which only has two stops, so doesn’t need quite so many).

3. They’ll have air conditioning.

Until now, deeper-running lines (identifiable by their low-ceilinged trains and the long escalators you take to get to them) have been unable to operate air conditioning. So perhaps the most important feature of these new trains is that they’ll offer what TfL calls “air-cooling”.

In the rendering video above, cool air is shown wafting down from the carriage’s ceiling.  Let’s give them the benefit of the doubt and hope this doesn’t just mean “air vents”. 

4. They won’t look that different.

The cars themselves will actually look a lot like the old carriages, bar a few design tweaks. One cool but essentially useless change is a new, neon-style strip of lighting at the front of the train. Inside, carriages will feature LCD screens showing advertising and travel updates.

Most of the changes seem to focus on doors: the carriage doors will be wider, you’ll be able to walk from carriage to carriage while the train is moving, and, from the promotional video, it looks like TfL are planning to install glass platform barriers in more stations, a la the Jubilee line.

Overall, though, the dated upholstery patterns, inward facing seats and not-quite-high-enough ceilings are all as they were.

5. They’ll be pricy.

TfL put a call out to companies interested in building the new trains earlier this year, and the advertisement indicated they’re expecting to pay between £1bn and £2.5bn for the 250 trains. So, potentially up to £10m each. That said, they’ll produce more savings – more passengers, less driver salaries – and are meant to last for around 40 years.

5. They won’t actually be in use for ages.

Companies will bid for the chance to produce the trains next year; the contract will be awarded in 2016; and the first trains won’t be introduced to the network until 2022. So a good few years left to bake aboard the Piccadilly Line, then, wishing the adverts were moving.

Renderings: PriestmanGoode.