How should the urban infrastructure be improved over the next 50 years?

Urban Infrastructure 

How should the urban Infrastructure be improved over the next 50 years?

There isn't, in my opinion, a fully inclusive response to this. If we greatly simplify things, there are/will be only two main categories of large cities.

1. Cities that are more or less steady, particularly in wealthy nations where the population is gradually increasing or decreasing

2. Rapidly expanding cities, particularly those in developing nations, which are going through essentially the same thing as the Council of Cities in Europe in the second half of the 19th century, only more quickly. These cities are experiencing extremely rapid growth and all the issues that come with it.

Global climate change will affect all cities, but each one will experience it in slightly different ways depending on its geography and climate. For instance, Mumbai deals with pollution, summer heat waves, and a rising sea level. On the other hand, cities like Berlin or Prague will have to deal with much more intense summer heatwaves (both cities are already quite uncomfortable for much of the summer, and some locals try to spend as little time in the city as possible), and in the later years of this century, they'll probably be "enjoying" the kind of thing we know from southern Europe - fires in the nearby forests, meadows, and fields.

I've always been in favor of compact, close-knit cities. Of course, this idea is only applicable in specific situations and at certain densities. However, cities like Mumbai, Jakarta, or Karachi are in a situation where they must manage the influx of new residents and not entirely practice "smart urbanism." What I find with these mega cities is that urban planners lack the experience to design them effectively because 1. They grow primarily with little to no regulations. 2. It is ineffective to add a lane to a motorway that is congested. These large cities naturally become too hot.