It is one of the last nice features on Garmin maps. Coordinates are plotted for tunnels and big underground overpasses sector. When you is driving in this sector the following events occur:
- switching in night mode as you notice
- simulation driving with speed what was before your device lose communication with satellites (GPS usually not work under ground if there are not GPS repeaters) !!!Be careful - you may stop in tunnels but vehicle icon will be move across the screen as long as the Nuvi does not understand that it was deceived (I often seen this picture in traffic jams in big underground overpasses)!!!