Starting a motor is much noisier than idling a motor.
It's "idle start/stop". not "idle stop". At some point the light will turn green.
Having stood next to many cars starting after an idle stop, the start is barely louder than the idle. The area under the curve is far smaller for idle start/stop than it is for leaving the vehicle running.
Having stood next to many cars starting after an idle stop, the start is barely louder than the idle. The area under the curve is far smaller for idle start/stop than it is for leaving the vehicle running.