Lexus autonomous prototype review

No need for a chauffeur. Just punch in the destination, sit back and relax.

It's approaching peak hour in Tokyo, one of the busiest cities in the world.

There are five of us in the car and we're all passengers, including the guy behind the wheel.

At the press of a button on the steering wheel our Lexus limousine takes over the driving duties.

The car will use cameras, radar and lidar to navigate its way onto and off one of Tokyo's busiest freeways

The only clues that the machine is in control is a display on the centre console that says we've entered automated mode - and the fact that the guy in the driver's seat has taken his hands off the wheel.

For the next four minutes the car will use cameras, radar and lidar to navigate its way onto and off one of Tokyo's busiest freeways, changing lanes several times along the way.

Lidar is the technology police use to book you. It bounces a laser beam off objects to work out distances and speeds. In this case its job is to measure the distance and closing speed of the cars in the adjacent lane and work out a safe time to merge.

The navigation part of the puzzle isn't done by satellite positioning because that isn't accurate enough for the task at hand. Lexus parent company Toyota has used a fleet of vehicles equipped with a combination of small sensors, cameras and GPS units to automatically generate detailed 3D maps of the roads we're travelling on.

The readout on the centre screen shows exactly what the car is going to do, as well as displaying ghost images of other cars it has detected in front and behind our car.

The readout tells us when the car will merge and whether it will accelerate or brake sightly when it finds its place in the stream of traffic.

It also shows whether it will need to accelerate to keep a safe distance from the car behind or brake to maintain the gap to the car in front.

In one corner of the display it shows a brake pedal, accelerator and steering wheel, with any throttle, brake or steering inputs highlighted in blue.

Toyota is aiming to bring products to market that will allow for driverless transport by 2020

Eventually we navigate our way on to the freeway, change lanes back and forth, take exit roads and turn corners, all without any human intervention. Then once we are off the freeway, the machine tells our driver to take over the wheel again.

Although it can slow and speed up on the highway, it can't bring the vehicle to a complete stop, although other existing technology, including automated city braking, would presumably take over.

Toyota is aiming to bring products to market that will allow for driverless transport by 2020. It's not the only one working on the technology, and there is an argument that it is actually late to the party.

Silicon Valley's Tesla electric vehicle already has autopilot functions and automated lane changing, while several of Lexus's luxury rivals can already take freeway bends at speed.

General manager of Toyota's future project division, Ken Koibuchi, won't be drawn on whether Toyota is trailing its rivals. But he says all systems are not the same.

"There are very many types of technology in this field... Our system is very accurate compared to other systems. So maybe other systems that release very quickly are not as safe as our system," he says.

The Toyota system is far from perfect yet though. At the moment the company has only mapped a limited section of Tokyo's enormous road network. Mapping the world is a much bigger challenge.

But if the car industry can eventually master the technology, it could eventually spell doom for taxi drivers and hire car chauffeurs.