"there's always one 
"....really ?
"So in future if you happen to be approaching a traffic jam/grid lock it would be possible to go to flying mode and continue your journey"
...not in this you won't.....you need a runway to take off and land....how will you manage that whilst driving around cities or suburbia or on a motorway with all those other cars around you when you happen upon a jam
At best, you could drive it to an airfield and then fly it from there....'
invention of the century' 