[crzwdjk]

It's a good question. Whoever is responsible for the road/bike lane should probably be doing some traffic counts to see how things are working out, but who knows if they've bothered to collect the data.

One problem with just going by your impressions is that cars take up an awful lot of space and a road can look full of cars, even if they don't represent a majority of people. On the typical NYC (or Boston) street, pedestrians outnumber cars 10:1, but get much less than half the space. For another example, the Dan Ryan Expressway in Chicago has 7 lanes in each direction, and two subway tracks in the middle. The subway can (and likely does) carry more people than all the expressway lanes.

Another problem is that in urban settings specifically, the capacity of a road is pretty much always limited by conflicting traffic at intersections, and so the exact number of lanes doesn't actually make a difference as long as it's enough to feed cars through the green lights at an optimal rate.