Lexus has taken the next step towards making the actual driving of your car an optional activity, unveiling its Automated Highway Driving Assist in Tokyo.
While Lexus safety engineers admit they don't like the term autonomous driving, they're happy to call their highly advanced prototype system a "copilot".
Switch your copilot on and you can take your hands off the wheel and feet off the pedals, sit back and look at the clever stuff happening on the screen. At this stage, the only task the human driver needs to undertake is lane changes.
The system combines two trick bits of technology, the first being Lane Trace Control, which uses cameras to read road markings and satnav information to steer around corners.
The car's cameras also watch the movement of cars in front of you and infers where the road is heading.
The system is twinned with something called Speed Management, which measures the cornering g forces on the car and slows you down to an appropriate speed (this can work in the background even if you are driving - if it feels you're approaching a sharp bend too quickly it will warn you).
Apparently 0.1g is the ideal level for cornering, an idea that more enthusiastic drivers might argue with.
The second system is called Cooperative Adaptive Cruise Control and uses car-to-car communication to ensure not only smooth progress for your car, but a more efficient flow of traffic overall.
Acceleration and deceleration information is shared between vehicles, so your car knows when the one in front of you is braking or accelerating, and adjusts its speed - meaning there's no need for sharp braking or the kind of surging that can make peak-hour driving so annoying, and fuel inefficient.
We took a ride in the back seat of an AHDA-equipped Lexus GS to see the co-pilot in action and were blown away by how effective it was.
Our driver used the Lane Trace Control, Adaptive Cruise Control and Speed Management to drive the car for him, through traffic and around sharp bends.
A sensor-equipped Toyota Prius then pulled in front of us and we switched to CACC, which perfectly mirrored the movements of the car in front to keep us at a safe distance.
The self-driving, or copiloted, car felt safe and extremely clever and a display on the screen tells you exactly what the system is up to.
Lexus says it will bring AHDA to market by 2015, but obviously the cooperative cruise control is a way off yet, because other cars - from other car companies - would need to be fitted with the sensors and the ability to broadcast the information, and getting rival car makers to agree on a set of standards will no doubt take many years.
Lexus says that despite the threat a copilot would seem to pose to enthusiasts, its philosophy is that it will "never compromise on the joys of driving a car". At least you'll be able to turn the system off if you want to have fun.
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