Zip line fire escape

This idea came to me as a way to avoid crowded sidewalks, but after watching a bit FOXchannel programming (footage of people jumping from burning apartments), it evolved.

The top floor of every tall building should be equipped with a dozen Zipline launchers. This would be a cannon that shoots a grappling hook out to the roof of another building, where fireman retrieve it and fasten it to something on that roof. Then potential victims of a fiery death can instead slide down to safety.

When the elevators and stairs are on fire, and there are too many people to evacuate by helicopter, an array of these tools could save many lives.