They are low frequency, bass tone sirens that emit vibrations that can travel up to 60 metres.
The idea is that if people aren’t pulling over when cops are using their lights and sirens, they can then turn on the howler and it will make the cars in the way lightly vibrate as a gentle reminder to move over.
I guess people use the excuse that they don’t hear the sirens because their radio is too loud, or they just don’t see the flashing lights.
There won’t be excuses if your entire car starts to shake.
Well, unless you think it’s an earthquake, but they you’d probably still pull over… we hope.