A city’s compactness is a compromise. On one side, a city can be spread-out — giving the advantages of cheap construction costs and plenty of green areas and roads, but also long commutes and dependence on cars. On the other hand, a compact city allows shorter commutes, better public transport, more services and nearby jobs, but suffers the disadvantages of overcrowded roads and noise pollution.

The primary issue boils down to roads. For roads not to be overcrowded, there must be plenty of them, and the population density cannot be too high. But when people's homes are spread out, their need to travel increases, creating congestion and the requirement for more roads.

The solution often employed when a city’s roads aren’t up to the task is to put some of them underground — normally major thoroughfares. This kind of retrofitting is not cheap, and is normally avoided when building new cities.


Traffic where it belongs - under ground! Source: Wild Rocket Sledge Ride

But what if we put roads underground from Day One? Just lay out the road system on level -1,-2 and -3, and then lay the “real” roads out on the level above? Cars could get all the space they need – zipping around underground – and people could enjoy sun and fresh air without having to put up with the infernal noise of traffic. The whole city could be one large pedestrian zone with shops, parks and green spaces built to a scale appropriate for humans rather than cars.

Expensive? Unrealistic? Not when building a new city from scratch, as some developing countries, such as China, are doing today.

If the site is a greenfield, building a concrete supported floor is not very expensive, as long as there is enough space to use proper tools for the job. If the buildings are tall, the additional expense per square meter should not be excessive.

The advantages would go far beyond making the city more pleasant. With roads underground, it would be possible to build more compactly while installing better infrastructure (you can have as many layers of roads as you desire!). More compact with better infrastructure means more people within easy travel distance, so the likelihood that you and your spouse can find a job that exactly suits your specialization increases. Likewise, your employer is more likely to find customers for specialized products. A large, ultra-compact city is likely to make its citizens ultra-productive, giving economic yields that will pay for the additional building costs many times over. More inhabitants pr square km will also make it cheaper for the city to supply services to its inhabitants, either it be electricity and water or policing and health services.

Now that we’ve convinced ourselves that we wish to build as tall and compact as possible and can do so while maintaining a pleasant living environment, why don’t we see how far we can pull the string? Let’s not just put one layer of roads in the ground – make it three! At the bottom we put thoroughgoing motorways and subways. Then we have a layer for cars, and above that one for buses.

But let’s not finish yet! Since we are building the whole city from a greenfield, we can install more gadgets than a sedate, mature city that is only slowly become dense. Let’s put in gondola lifts between some of the tallest buildings, creating a web of continuously moving lifts that you can hop on without having to dig out a timetable before leaving home. Placing the stations at somewhere between the 30th and 40th floors could be suitable, and at around the same level we can put in public shopping floors interlinked with bridges between the buildings. This way we would get two levels of shops while creating an effective way of moving shorter distances: Take the gondolas a kilometer down the road toward your destination, then walk the last distance by foot. This “skystreet” should be linked with the street level by public lifts. Again, since all this is installed when the buildings are built, the additional cost will be moderate, and gondolas are quite capable when moving large numbers of people shorter distances.

To complete the city, decorate it with plenty of trees and green. Plant trees at street level, but make the rooftops into parks, too. Now do we have a dense city that rivals suburban life?

Bluesteel is a mechanical engineer and MBA graduate from Norway, employed in the oil industry. When he is not blogging, he enjoys skiing in winter and bicycling in summer.