They call it the 'Heathrow Pod', and it is a new way of getting around the urban jungle. Rather than waiting for a bus, business travellers just take one a futuristic taxi.
Fraser Brown, the managing director of Ultra Global PRT explained: "It's a PRT system - a personal rapid transit system. And what these vehicles do is they work autonomously on a guideway to take passengers from the Business Car Park at Terminal 5 up to the main terminal building, ready for their flight.
"Here you've got a system with 21 vehicles which are working truly on demand. You come up to them, in the same way that you might approach a lift lobby, you press the button and the doors open and away you go."
It has taken a decade of development to perfect the system, with the pods benefiting from input from several EU projects. To make the pods reliable the team uses existing technology, such as regular car tyres.
Adam Ruddle, the head of vehicle engineering at Ultra Global PRT, said: "The batteries we have come from Spain; they were already in production when we talked to the manufacturer. The motors were manufactured in Italy, and were being used on electric vehicles already."
The control room keeps an eagle eye on the pods as they trundle around happily without rails, calculating where they are as they go.
Adam Ruddle explained how that works: "The vehicle measures the rotation of the wheels, so it knows how far it's gone. And then it uses laser sensors to measure the distance to the curbs on either side of the track, and that allows it to recognise its steering position."
Reliability is over 99 percent, but there are still some factors the engineers did not foresee, including the way passengers behave.
Adam Ruddle said: "When we were sitting, working out where to put the buttons inside the vehicle, we all sat bolt upright, very correctly in the seats, and the buttons were in the perfect position. What we find now is that people relax in the vehicles, they turn slightly, they lean to one side, and we end up with shoulders pressing against the buttons."
The Heathrow Pod is unique in Europe. With a smooth guideway and no high voltage cables it is at least three times cheaper than a normal light railway.
Fraser Brown of Ultra Global PRT concluded: "What we want to do going forward is to take technology from other sectors like the automotive sector to really improve the system operability and reduce the cost even further."