A camera mounted in front of the rear-vision mirror snaps the relevant speed signs, and changes it accordingly on the heads-up windscreen display.
This happens most of the time, although occasionally the camera or sensor misses a sign and doesn't adjust the relevant speed limit.
Responsibility for the speed of the car obviously remains with the driver, who cannot complain they were misled by the system - if the driver doesn't notice the actual speed limit signs then they shouldn't be driving.
In addition to the speed limit, the heads-up display in the BMW provides an abbreviated version of the directions programmed into the GPS system. This is an arrow pointing in the right direction, along with the distance to the next intersection.
There is also a full display showing on a screen in the centre of the dashboard, including an estimated time of arrival.
Entering the destination is easy using the central I-drive toggle and mouse-like device sitting between the two front seats.
In the BMW it is easy to lock in a destination, and the system gives the driver the option of choosing the fastest route, an Eco Pro economical route, and a third "Short" option suggesting a short as feasible but on fast roads route to your destination.
The system can display a map view, a north-oriented view, the direction of travel view, and a perspective view, which features landmark buildings in 3D.
The system can also be programmed to warn the driver of traffic congestion ahead, a feature particularly useful in central Auckland.