Airships as public transport Yay or nay?

[Murk]

Could you make guided aircrafts?
Say, a blimp or zeppelin that is connected to a line or chain to guide it and keep it steady? Updrafts, head winds and stability would all be much less of an issue. Just like trains, the airship could make easy and regular stops at specific points. They wouldn't even need to take off or land, just always stay afloat.
It would be like a subway, or a train, but flying over (or under) the rail/line instead of rolling on top of it.

The benefits compared to a train would be that they could make high-altitude lines without a heavy supporting infrastructure - I think a taut chain spanned between buildings could already function as a guide for a small airship. For a big metropolis this would evade all the problems with subway lines - no digging, no tunnels, not trouble bypassing existing buildings: simply span a line or rail between two points and attach small powered blimps to the line with some sort of pulley system.
I'm thinking it might even have less friction than a train or subway track. I know a lot of ferries that are guided by actual chains underwater (the ferry just floats and is pulled across the water by the chain). I imagine these airships would be similar, but instead of floating on water they float in the air.

Just throwing it out here. Would this be viable? Would it be vastly more expensive than building an entire subway system? Any problems I have not foreseen yet?