osiris4isis when You drive (in real life or in simulation) in lower left part of the mapscreen You can see current speed limit for this part of the road. In Europe it's a red circle with number inside it, in USA it has a square form. On my nuvi 3597 now installed two speed allerts: Cyclop and your's custom one.
When i drive close to speed-limit allert point, this two files do different things:
- Cyclop draw alert symbol, make sound and draw red colored text at upper part of screen.
- You file do much more: it can draw allert simbols on the map, play sound, draw gray text on the top of screen BUT ALSO change speed limit on the current part of the road. And on the screen we now see speed limit from You file, not implemented to the map by Garmin/Here/NavTeq.

On my screenshots i try to show: when i enable only Cyclop, this road have 60kmh restriction (left one), but when i enable Your file, same road speed restriction changed to 15kmh (right screenshot). Other word, Cyclop only show, You file can change the world
And i don't know (need to test), may be it also change a calculated road, because if some part of roads change inner limitation from 60 to 15, nuvi may find faster way by using other roads.