Does my GPS work when I drive into a tunnel?

Your GPS receiver requires intervisibility with the GPS satellites. Thus the GPS system does not work in tunnels.

MOTONAV will show you a symbol as soon as you enter a tunnel and have no GPS reception. You will also hear a speech announcement upon entering the tunnel concerning the next maneuver (i.e. "In the tunnel take the second exit"). This direction will remain on your phone's screen for your orientation until you leave the tunnel.