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How to use these walls?

Hongkong has a lot of high rise buildings. Many of these has a high wall with almost no windows. (Examples, more and etc)

These walls are typically located in public housing. If these walls can be converted into tall hydroponic green houses, they can provide food for those living in these public housing and provide local jobs. Am I right?

Straddling Bus

Think about it. A bus which allows other cars to pass under it and can be deployed relatively fast (as compare with building subway) and flexible enough to run on most roads. This is China's huge bus, 4.5 m wide and 6m high.