Mate just fiddling again and I noticed that when on route in simulation mode if I tap the screen again it will take me to an overhead view. This has a circle around the car which I presume triggers the alerts as they go off when it hits the sweet spot. If in simulation mode and trying to set location if you zoom in on the car a couple of times you will find this same circle around the car. Its also possible that alerts will become dependent on accuracy of gps at time of passing alert
Paul