[thomaslkjeldsen]

One way of looking at it is to consider the area of road required per citizen during transportation. If a car consumes 10 square meters of road and a bike only consumes 2 square meters of road, converting a car lane into two bike lanes should immediately reduce traffic congestion. If and only if, of course, enough people are able and willing to do so.

[bluGill]

Cars can go a lot faster than a bicycle (assuming safety is a concern, there is a reason I don't have a motorcycle - which isn't to say cars are safe) thus per unit time you can get more distance in a car. Which is back to my point: you are throwing away the point of the city with that argument. I realize parking takes more space, but it will be ages before the city rebuilds to the new reality and until then it isn't functioning like it should.