Why does an automatic car move forward on its own when you take your foot off both pedals?

Question 2: it started as a side effect and became a deliberately preserved feature, which is why electric cars imitate it.

The useful things creep does, once you notice them:

• Parking and manoeuvring at a speed below what the throttle can control smoothly. Reversing into a space at walking pace with only the brake is far easier than modulating power.
• Hill starts. Creep partially holds the car, so the roll-back gap between brake and throttle shrinks.
• Stop-start traffic, where you can move a car length using only the brake pedal.

Drivers turned out to rely on it heavily without being able to name it, which is the strongest kind of feature.

The part responsible is the torque converter, and the short version is that an automatic has no clutch to disengage — it is connected through a fluid coupling that never fully lets go.

Picture two fans facing each other in a sealed housing full of oil. One is driven by the engine and throws fluid at the other, which is connected to the wheels. At idle the driven fan spins slowly, so it throws fluid gently — enough to nudge the second fan, not enough to accelerate the car. That nudge is the creep.

Which is also why it stops when you brake: you are simply overpowering a weak coupling, and the engine can idle against it indefinitely without stalling, because nothing is rigidly connected. A manual stalls in that situation precisely because it is rigidly connected.

So the answer to question 1 is: it is not a clutch, and a fluid coupling has no fully-off position.

For question 3 — yes, and it is entirely artificial.

An electric motor at zero throttle produces no torque and would simply sit still. Early electric cars did exactly that, and testers and drivers found low-speed manoeuvring unnerving: the car felt like it might roll away, and precise parking took real concentration.

So manufacturers wrote creep back in. The software applies a small amount of torque when the car is in Drive, the brake is released and speed is near zero — a deliberate simulation of a mechanical accident from a technology the car does not contain.

Most let you switch it off, and it is usually paired with the one-pedal driving setting. Worth trying both for a week: people are split, and the ones who dislike creep tend to dislike it strongly.

One safety implication worth stating since this is a learner question: because creep never stops on its own, an automatic in Drive is always trying to move.

That is why the habit of putting it in Park with the parking brake on matters more than it does in a manual, and why footwell obstructions are more dangerous in an automatic. A car that only moves when told to fails safe; a car that always wants to move does not.

Not a reason for concern, just the reason behind a rule that otherwise sounds like fussiness.