Finally this thread takes a turn towards what I do for a living!

To make heads or tails of what is the right thing to do, we must first establish if HK airport is to be run as a government owned undertaking or a private one. For the time being, it is firmly held by the goverment. Many governments try to avoid being caught up as owners, by making it a limited liability company or other structures, but when they are the controlling owners - it is a government undertaking.

This means that the standard project evaluation done in private companies no longer suffices. Governments are, by their very definition, tasked to look after more than the bottom line. They are to take care of their citizens' rights, the environment, the bio-diversity, etc. Not an easy job!

But one thing comes shining through: If they are to do this evaluation properly, then they do need to put a price on what they lose by expanding. This is similar to the exercise done in most countries when considering where to place a new road, for example. Stonecutter's Bridge was likely never put to this test.

Looking at the third runway, what factors are there to consider - beyond the purely financial? And how to cost them? That is where HK government needs to bring in some credible expertise. Once you add it all up, it would surprise me greatly if the public ever sees a return on investment. Will that stop HK from pouring ahead? Nope, not for a second. Is it wasteful? Hugely.

HK has a not-so-proud history of chasing ghosts, like new container terminals, bridges and amusement parks (ROI for Disneyland?). I'm just waiting for the posters to arrive: "Runway 3 - add to your flying excitment!" or "A new runway for more airborne titillation". And all with a new shopping centre as the piece de la resistance, just like the sad story in T2.

If they are serious about analysing this properly, there are solid frameworks out there from IFC and others. It would be really interesting to see the payoffs from the third runway in such an analysis!