"'if road = tunnel then {assume I'm moving at the same speed along the road I was on when I lost sat nav signal}"
Which wont work too well in the labyrinth of roads under the city centre where I live.
"'if road = tunnel then {assume I'm moving at the same speed along the road I was on when I lost sat nav signal}"
Which wont work too well in the labyrinth of roads under the city centre where I live.