> Who really imagines that transit is going to double in size,
> or even that highway use is likely to reduce?
Well, we have a little experimental data for this: the 1989 Loma Priata earthquake closed the Bay Bridge for 6 weeks. At the time, about 250,000 vehicles per day used the bridge, and BART carried about 218,000 passengers. Within a week, average ridership was 308,000 per day; current ridership is 340k/day ("official" capacity is about 350k, though the all-time record was 381k ... which means if we have another one, we're well and fucked).
So there's a significant transit system that has doubled in size in not too many years.
> More likely, it will continue to increase.
It's true that the more successful a region's transit infrastructure is, the more interesting it is for people to move there and to make a living there. But: it's better for the planet if the new arrivals aren't 100% car commuters, no?
/jordan