Back to the 50’s and 60’s, cars were produced with simple mechanisms which had a bit advanced features of technologies and uncomplicated ignition switches. Drivers even could leave the key out of the car while it is running without worrying about the affection to the engine’s operation. But now, we are living in a modern world and the cars are also made with more advanced technologies including their key functions.

1. What will occur if the key of the car is removed while driving?
Frankly, nothing will happen because it is impossible to take the key out. For security reasons, the ignition switches’ structure becomes more and more complicated. In modern cars, you can’t take the key out once the engine has been started. Even when you can remove the key as a result of some defect, the steering wheel will be locked immediately while the vehicle is running, which easily causes an accident.

If this is done when the ignition switch is off, the steering wheel shall be locked and then the gearbox will turn to the Park mode. As a result, the car will stop. This will be very dangerous, especially when the car is running on an expressway or a heavy-traffic road.

In modern cars, you can’t take the key out while the engine has been started

If the car has an electrical-based support which may consist of steering and braking system, it will stop almost right away. If it works with a vacuum-based support, its engine will operate for a moment and continue spinning until it stops completely. So if you can get the key of the car out while driving, a crash is the most likely consequence.

https://www.youtube.com/watch?v=ZSxubcxxXS4
What happens if you throw out your key (fob) WHILE driving? Don't be stupid enough to do this.

2. How about in an advanced car?
A number of cars today do not even have ignition keys which are functioned by RFID fobs. The fob must be within a certain range to keep the car running smoothly. The vehicle will still run in Park mode, even when the RFID fob is a little out of range.

What will occur if you throw the key out the car window while the car is in a fast motion? If the car engine is operating and the Park mode of the gearbox is not turned on, the car will keep running. The central computer system of the car will assume that the fob is functioning improperly. Therefore, the system will not force the engine to stop for safety reasons.

The vehicle will start or in Park mode, even if the RFID fob is a little out of range
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https://naijauto.com/safe-driving/what-will-occur-if-the-car-key-is-taken-out-while-driving-339