Thanks tboy. I note that the study clearly focusses on the empty seat factor for all modes except cars. I'm sure you enjoyed that eight passenger Airbus, but if ViaRail, Amtrak, Greyhound and the TTC were as good at packing passengers into trips as the airlines usually are, their emissions per passenger mile would drop considerably. That is the point of the article: empty trips cost. Which is what I think every time I look at a packed road and realize there's just one driver and four or more empty seats in almost every vehicle in sight. Now just imagine the million and a half daily TTC riders all buying cars and demanding road space and tell us we can afford to bulid it, it'll be cheaper. Really.
As for supporting infrastructure costs, that's a hugely vague and grey area. Do we factor in the airport to city centre railway as a cost of the airport? What proportion of the city centre to airport roads do we charge against the airport if we don't build the train? The asphalt roads we drive on would be there in some form, unpaved perhaps, if we had no cars. Do we charge them to 'general existence of people' call them amortized, and charge only the paving to car usage? For all that we want those numbers to be objective, they all depend on so many human, value-driven choices that they're inevitably political. Which means they have at least as much to do with popularity as practicality.
Consider a Parisian boulevard. Three or four lanes of traffic both ways, a wide landscaped strip each side, then two or three lanes used for parking, more landscaping, then a sidewalk wide enough* for cafés and whole groups of strollers to share. University Avenue isn't wide enough to qualify. Napoleon's commissioner of roads dynamited whole neighbourhoods to put them through—for pedestrians and carriages—and was hated for it. But although Parisians are as divided about cars as anywhere else, now they love the Boulevards and no one can imagine Paris w/o them. So how do we cost out that sort of infrastructure? It'll always be grey, it'll always be political.
It's what keeps society going, and ultimately that is a benefit, not a cost. But garbage abandoned for someone else, however much or little there is, that's a cost.
Now aren't we supposed to be talking nekkid pitchurs?