In this question, a "car" has a combustion engine. Regardless of make or model I can almost always recognise the sound of a car backing up. This sound is distictly different from when the car moves foreward and the difference in sound seems to be the same for all cars.

Is it the gearbox? The transfer? The differensial? The engine runs the same way regardless, so it shouldn't be that, right?

If all road vehicles were electric, I'd like to know how much electrical power would be consumed ( and how many more power stations would be needed ) to keep things running at more or less the same levels of traffic as today. . .