First proposed in the 1970s, and with work starting in 2009, the 73-mile Crossrail project, now named the Elizabeth Line, is finally opening its full route to the public next year.

The line, running from Reading through central London and on to Shenfield, has cost nearly £15bn to construct, and will see the opening of nine new stations in central and outer London, serving as a new commuter route for millions of Londoners.

This month Transport for London (TfL) and commercial partner Exterion brought the proposition to market, with a unique approach to advertiser investment.

Rather than buying the route as part of the wider Underground network, brands will, at first, only be able to buy ad space on the Elizabeth Line through a partnership package.

At a proposed cost of £6.5m per advertiser, six launch partners are guaranteed sector exclusivity for the first 12 months of operation, as well as a proportion of the advertising estate on stations and trains (including large-format digital, small-format digital, digital escalator ribbons and train panels). Compared to the current TfL inventory, ad space will be high-tech and state-of-the-art, with 90% being digital panels.

Brands will also receive exposure through TfL’s own website and marketing, with brand logos throughout, including a presence on all versions of the tube map.

The line will carry 200m passengers per year – comparable to the Victoria line, which is currently the sixth busiest line on the network. It will bring an additional 1.5m commuters to within 45 minutes of the city centre and will also be responsible for transporting tourists, expecting to carry a similar proportion of international travellers as the rest of the network (approximately 28%).

While Elizabeth Line sites will not appear on Route – the UK’s outdoor audience measurement system – until mid-2019, it is estimated that in the first year it will reach 4.7m unique adults at a total OTS of 140.

Our view is that it is a difficult time to come to market with such a proposition. While the scale of investment means that it’s likely this will be funded via a corporate sponsorship rather than media budgets, asking for this large a sum is ambitious. Recently, the openings of Heathrow T5 and T2 and the re-launch of the Piccadilly Lights all had difficulty finding long-term commitment. It feels likely that, ultimately, this will instead be sold as smaller chunks of inventory.

From a planning perspective, the audience can be reached more efficiently through other environments. However, this is a sponsorship opportunity, and the value potentially delivered through the association with the Elizabeth line and all it represents should be considered – investing in London and being at the centre of state-of-the-art infrastructure that will transform the way people move around the city.

Another consideration would be the management of the creative messaging throughout the day, week, and year to continually engage and entertain travellers.

If the rationale for investing in London in this way has appeal to an advertiser, and the creative and amplification mechanics can be realised, then there are few opportunities of this scale and stature.