By Lucy Rodgers

BBC News



Personal rapid transport vehicles travel at 25mph

There are no drivers, no rails, no timetables and no emissions. But, most importantly for passengers, there are no queues.

Welcome to the UK's first personal rapid transport system (PRT).

But while these low-energy, driverless pod-shaped vehicles may look like something from sci-fi epic Bladerunner, they are about to become British transport reality.

In less than two years' time, after the opening of Heathrow's Terminal 5 in March 2008, a network of 18 of these four-seater capsules will be ferrying passengers to and from a business car park to the new terminal building.

Already under construction, the first phase of the airport's £25m PRT will use 3.8km (2.4 miles) of guideway - designated ground-level or raised path - to move people from car to check-in in just four minutes.

No wait

But the greatest selling point of the system for users is not its speed - set to a maximum 25mph (40kph) - but, instead, its promised convenience.

It appears to solve the often-encountered problems of mass public transit, including fixed timetabling - leading to long waiting times and queues, restricted routes and shared travel space.

See proposed route of Heathrow personal rapid transport system

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With PRT, vehicles turn up on demand, can be programmed to go to any destination and accommodate just one group of travellers who already know each another.

According to Advanced Transport Systems (ATS), the Bristol-based company behind the Heathrow system, passengers will only have to wait a maximum of 12 seconds.

And, because the vehicles have their own designated paths, there will be no congestion and no traffic lights - in principle, a non-stop journey from A to B.

To those with more green concerns, the system also has the advantage of generating zero local emissions and being 70% more energy efficient than cars and 50% more than traditional buses.

"It offers a completely new form of public transport - one that will deliver a fast, efficient service to passengers and bring considerable environmental benefits, saving more than half of the fuel used by existing forms of public or private transport," says Mark Bullock, managing director of Heathrow Airport.

So, how does the system work?

The cars, powered by a battery pack, follow dedicated 1.5m-wide guideways using laser sensors embedded in the vehicles.

Passengers board at designated points - not unlike bus stops or taxi ranks - where vehicles are waiting or can be called within seconds.

Expansion

Once on board, travellers use a touch screen to select a destination. A central control system responds by allocating the vehicle the required path and passengers are taken non-stop via the best-available route.

This, ATS says, is "a new approach to travel. This is transport for a sustainable future."

If the first-ever public test of the technology at Terminal 5 goes well, Heathrow plans to expand its use across the airport.

The cars can be caught at designated points

But it doesn't stop there. There are already indications that the capsules will be embraced elsewhere in Britain and the world.

In the Northamptonshire town of Daventry, councillors are considering proposals for a PRT system of up to 100 vehicles to help transport its growing population, which is expected to increase from 23,000 to 40,000 by 2021.

And a number of other countries, including some Gulf states, are also looking at similar systems.

However, although PRT seems to be an ideal transport solution, critics claim it has limited applications, especially in big cities due to the required network of guideways. Some also say its efficiency has yet to be tested.

City dynamics

But, those behind the Heathrow project acknowledge PRT, a concept which has been around since at least the 1950s, has its limits. They say it will not compete with mass transit systems in large cities, such as the London Underground, but will instead complement them.

Richard Teychenne, of ATS, says it will work particularly well in the suburbs, linking areas together - such as transporting people between residential areas, or from rail stations and out of town car parks directly to shops and offices.

"It could really change the dynamic of a city," he says.

Another advantage of the capsules, he claims, is safety.

CCTV can be in operation in every vehicle and passengers no longer have to share public transport with other unknown people. This could offer obvious advantages to women as well as children travelling to school, he says.

When all its features are digested, PRT may sound like public transport too good to be true, and it remains to be seen whether it can deliver on its promises.

Mr Teychenne admits the rollout does depend in how things at Terminal 5 go, and all international eyes will be on the west London airport in 2009.

"Heathrow is setting a marker for the world," he adds.