How could we replace the capacity of the NYC subway?
frumin.net
frumin.net
http://img8.imageshack.us/img8/9346/espaciocoches.jpg
It shows how much space it takes to move the same number of people using cars, bus, and bicycle.
You can fit 4 people in a car, but you can not load a bus completely full or no one will be realistically able to use it.
So the poster should have between 1/4 and 1/8 the number of cars on the screen.
Meanwhile, most cars have only one person in it. Maybe an average of 1.5. You could have a carpool with 4 people in it, but I think that's rare compared to single passenger vehicles.
Interesting mildly off-topic side-note (gathered from 'The World Without Us'): if the systems responsible for actively pumping water from the subway system were to shut down, the subways would be flooded in about 2-3 days (since they're well below the water table of the surrounding Hudson and East Rivers).
http://www.nytimes.com/2009/08/01/nyregion/01hot.html
"One reason for the record-breaking low temperatures was the record-breaking rainfall and accompanying cloud cover. The deluge of more than 16 inches (twice the average amount) made it the second wettest June and July on record, edging 1928. The wettest June and July was 1975, with more than 19 inches."
(First reference I could Google up.)
There was a study about how building more than 3 lanes of highway did nothing to reduce congestion, because more people then just drove. (It's hilarious that you'd need as many tunnels into the CBD as West-East streets!)