UK transport app Citymapper is launching a new taxi service. Or, wait, a new bus service. Actually, it’s somewhere in between. After confusion this week when the company’s plans leaked to the press, Citymapper has shared some details of new “Smart Ride” initiative —  a hybrid service that will see a small fleet of eight-seater vans offer rides around a number of routes in London, changing their course based on customer demand.

“It’s a bit like a bus because it has stops, it’s a bit like a cab because you book it and it has guaranteed seats, and it’s a bit like a metro because it has a network of roads,” Citymapper’s president and head of business, Omid Ashtari, told The Guardian.

Smart Ride will only operate in a small portion of central and north-east London to begin with, with each ride hailed via Citymapper’s app. The key selling-point though is the company’s use of flexible routes. As customers hail more or fewer rides from different parts of the minivans’ catchment area, it will redirect drivers to meet demand.

This was the same idea Citymapper wanted to try with its experimental bus service, launched in London last July. But, the vehicles’ ever-changing routes proved too much for transport agency Transport for London (TfL), which had to vet each new itinerary. “It took us only one weekend before we learned enough from operations to want to change how we ran the route,” wrote Citymapper in a blog post. “We had to wait weeks before our change was accepted. It’s hard to innovate and iterate on such timelines.”

So, Citymapper applied for a taxi license and is now trying the same basic flexi-route idea with Smart Ride. (This taxi license also led to some outlets claiming the company was going to “take on Uber,” although Citymapper disputes this interpretation.) Will minivans beat out buses? Citymapper think it’s worth a shot.