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Would it be safe and legal to design a car which uses only power steering and where the steering wheel doesn't have a direct mechanical effect on the wheels?

I say that because If i was Elon Musk, I would make only undertrains for cars that you could put any old car onto. I would have a 1982 ford sierra, on an electric undercarriage.

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The system you are talking about is called steer-by-wire and has been attempted in the past. The only vehicle I'm aware of which has attempted it was the Infiniti Q50, but it seems after negative commentary, the systems were removed for a traditional column steered version.

Certain systems in the car such as the throttle and brakes have been brought over to a strictly drive-by-wire system, where the computer controls the workings of each. These systems bring a lot of weight savings into the vehicle and therefore make the vehicle more efficient.

There have been vehicles which are partially steer-by-wire, such as the GM full size pickups & SUVs with Quadrasteer, which allows the rear wheels to be turned by the computer in certain situations to allow for tighter turning and crab-walking the vehicle while driving.

For legality purposes, it really depends on where you are at in the world as to whether it's legal. It is illegal in many countries (as Solar Mike points out about the UK). Other countries may not be as strict about whether it can be used or not. Realistically, it will take a lot of testing and trials before it could be realized in any country. I would like to point out, though, many airliners to include the Airbus A320 and Boeing 777 are both fly-by-wire systems. If they can do it for airliners, it probably wouldn't be too difficult to do it for automobiles. Consumer acceptance of automobiles may be a bit tougher than airliners, though. Many people have no clue (nor do they want one) about how an airliner works. They just leave it to others to figure it out and as long as they stay in the air, it's all good. Since people control vehicles directly, they want to have more control of the vehicle (whether real or perceived). Just like airliners, cars would need redundant systems to ensure they continue to function correctly under any circumstances.

  • "If they can do it for airliners, it probably wouldn't be too difficult to do it for automobiles." – I don't think this is true. The effort required to make this safe is freakishly expensive. It only pays off because even small weight savings accumulate large cost savings over the multi-decade lifetime of an airliner. I'm not sure whether automobile drivers are willing to pay that price. Note, however, that cars have one important feature that airliners don't, which may allow the systems to be less safe and thus less expensive: they can just stop in the event of a problem. – Jörg W Mittag Dec 10 '17 at 23:04
  • Re: "freakishly expensive": airliners typically have up to quintuple-redundant control computers, developed by at least two independent companies based on two different hardware platforms, running two different operating systems, connected to triply-redundant data busses. – Jörg W Mittag Dec 10 '17 at 23:05
  • @JörgWMittag - That's what Infiniti did with the Q50 I mentioned. They had three redundant electronic systems, then if they fail, it does have a direction connection to fall back on (which is never in use unless electronic systems fail). – Pᴀᴜʟsᴛᴇʀ2 Dec 10 '17 at 23:08
  • Considering how automatic the wheel balances are in cars that change torque based on the wheel positions, steering wheel columns are as redundant as power-steering is powerful, they probably didn't give the motor enough precision and some inertia to the virtual steering column, it's a pity that they gave on the first attempt with Q50, rather than upgrading it. – com.prehensible Dec 15 '17 at 16:43
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The UK Construction and Use regs require a mechanical connection for all motor vehicles used on the road except for some agricultural machines.

In fact, for one of our “bend in the middle” or articulated tractors the “game” was to count how many revolutions the steering wheel did during the day as it was hydraulic only and the system had creep.

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