Copenhagen has become the model for making streets bike friendly. I went there about 15 years ago as part of a construction and city planning tour to check out the city and it was amazing. At the time they had a 15 year plan to drastically reduce their cars and turn the city over to pedestrians and bikers.
Now 15 years later they are reaping the fruits of that long term vision. Their city is amazing to move around in as a wlaker or biker.
Brooklyn and Manhattan are perfect for a similar conversion. We have a very compact building grid that makes it very easy to walk or bike pretty much anywhere. The biggest impediment is the noise, dirt and danger of the cars. Reduce the cars and it becomes really a great place to live.