I'll explain what this map is for below, sit tight!
There has been a lot of talk, especially over the last year, about adding protected bike lanes to 5th avenue and 6th avenue. There are currently unprotected lanes on 5th avenue below 24th st and 6th avenue below 42nd st. Transportation Alternatives (TA) has been pushing since 2012 and there has been some good activity in the community boards.
Despite all of that I think there are a lot of people who don't realize how difficult it is if you live in midtown east or higher to safely get to the lower parts of the city. The main issue is second avenue, which is wide, fast moving, and only has a shared lane—which cars rarely respect—until 34th st. Making it even worse you have to deal with commercial traffic and the chaos that is the entrance to the Queens-Midtown tunnel.
To avoid second avenue while still staying in bike lanes means biking all the way across the city to broadway (which is patchy and packed with tourists) or 9th ave. When I'm commuting I generally just continue on to the Hudson Greenway since I've already come so far, and it's the most safe riding experience.
All of this is to say that we need a better southbound bike lanes in central or eastern Manhattan. The reason that I think 5th ave/6th ave make the most sense beyond the reasons given by TA bring us back to my map above.
I've taken the NYC data on truck routes and overlayed it onto a map with bike lanes. You can see on the map that the 2nd ave shared lane is also an route for trucks, making it even more dangerous and intimidating to ride on. 5th avenue and 6th avenue are largely free of truck routes, and there isn't a better option which runs continuously downtown and is one-way.
In order to encourage more bicycling we need to have a connected network and people who are riding on the street need to not be scared by big trucks rolling by them at high speeds.
If you'd like to help TA has a page about this issue. They can also always use donations to help support their advocacy. Even if you don't bike or want to bike, protected lanes slow traffic and make it easier and safer for pedestrians to cross the street.
I'd like to thank CartoDB for making the amazing software that let me easily create the map.