The current behaviour is, that as soon as you blip a car, it pulls over. So you usually turn on your lights when the car is already pulling/pulled over, which feels strange.
Turning on the lights before also has some side effects, as the AI's logic kicks in to make way.
* Blipping a car does not initiated the traffic stop immediately
* Player needs to turn on lights and/or siren for the blipped vehicle to pull over
* Optional: This could also be combined with automatically turning off the siren after a short time (siren blip)
* Holding pullover button and/or time and/or distance cancel the traffic stop ..Even if not yet initiated
* Just in case you see someone else doing something worse or a call comes in