Capacity of a transport line, again

city_structureThe problem

The acceleration of urbanization is a fact that no one can deny. More and more people move from areas with a low-density population areas to the high density zones. The first category includes villages, small towns built during the coal industrial era, hamlets in the mountains, and so on. The second category, which gains acolytes every day, includes big towns, with at least 500.000 inhabitants in the central disc, and  with a population  of the metropolitan area numbering the lower  millions in the near rim and up to or even more than 10 million in outskirts. After all, city development is the business of the mayor and as such it has great importance for the future of the community. The costs are going up and recent events have shown that cost cutting strategies in very large cities are a double edged sword.city_pressure     As illustrated in the picture nearby, there is a certain pressure from the outside. The demography evolves on at last two axes:

  • the increase of human population
  • the accretion of people

The accretion is the concentration of people around the center of the city, according to the offer. Sometimes, new buildings appear just to accommodate the needs.  In other cases, there is a real long-term strategy of evolution for a given city. Most of the times, short-term decisions  with consequences in less than a year have to be taken.

city-satellitesThe solution

Back in the 60’s and 70’s, the stakeholders, like the mayors,  had less immediate worries and could focus on long-term plans.  With an  urban population less than 50%, there was enough space and time for future development.  And, surprisingly, the solution was not to increase the population of a city already big enough, but to scale up the density of population of the metropolitan area. This is the beginning of satellite towns, some 20-30 kms from the center of the large  city. New towns appeared overnight, with much space around them.  People preferred small individual houses at affordable prices to the high rise buildings downtown.  The quality of life was good.

Then the 2000’s came and the pressure was felt again. The big city was an undisputed magnet. After all, the real economy was happening there, downtown, not in the small satellites.  So, on one hand, we have the development of the large metropolis where people work, where we have the shopping centers, the downtown, and so on. On the other hand, we have the quality of life.  Both cannot coexist together and yet, they are part of the ecosystem.

satellite_linesThe transport line

The people from the small cities need a mean of transportation to / from the big city. We are not talking here of national railway, but of local trains, light rail, and subway extensions. In the image here we have a big city (the green circle), surrounded by  smaller towns. The three train lines connect all the cities. It is obvious that people move between the cities.

In time, not only the population of the large city increases, but that of the smaller towns, too. In such a case, the three train lines need to carry more and more people. Opposed to that is the maximal capacity of the lines, which has been discussed in a previous article. This is a problem many modern metropolitan areas  face today. It is not easy. The urbanisation has triggered an increase of the population along the train lines. What to do ? Build new ones ? Improve the existing ones ? Innovate ? The answer in another article.

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