In some ways it is hard to know what to make of the hutongs from an environmental perspective.
This is a true example of horizontal density, where people are packed relatively tightly into a small area.
Alan told me that there were now six million cars in the city — the number rising because motor vehicles are seen as a symbol of wealth.
In addition, if this was adopted in advanced economies it would be difficult to gain enough density to offset greater energy consumption with a single floor of living space.
Even in Beijing these neighborhoods are steadily losing out to vertical development.
The government is seeking to preserve the hutongs that I traveled through in the north, but some poorer hutongs I biked through in the south have been targeted for redevelopment.
Alan suggested that in the past several decades more than three-quarters of the original hutongs have given way to taller buildings.
As an environmentalist, however, I would be happy if any American could come close to matching Beijing’s existing transportation mix.
We started the day biking through the traditional hutong neighborhoods north of the Forbidden City.
Even better, on the busiest roads these are fully segregated cycle tracks — meaning they are separated from traffic by a physical barrier.
Recent studies have shown that this can lead to increased safety because motor vehicles are excluded from this part of the road, although intersecting traffic at major cross-streets remains somewhat dangerous.
Why do people immigrate to and from different parts of the world, risking all that is familiar to them, sometimes leaving their families, and most always most of their possessions?