Posted by: senjmito | November 22, 2010

Agglomeration: the magic role of mass transit in the city

Another thought-provoking piece from Paula Warren…

I sat at the railway station early this morning waiting for a train to Paremata and watching the commuters arrive. As each train pulled in, a stream of people poured out, filling the concourse. And I imagined what Wellington would be like if all those people were in cars instead of using mass transit.

“Agglomeration” is something that economists talk about, and that is used (or misused) in cost-benefit analyses of transport projects. Essentially, the more people and businesses there are in your immediate neighbourhood, the more economic exchanges you can easily undertake. This applies not only to intended exchanges, such as contracting another firm to provide a service or buying flowers from the florist, but also unintended transactions, such as running into someone from another company in the street and talking to them and discovering that there is an interesting seminar at the university that night.

Economically successful cities have high agglomeration rates. They also have a design that makes economic exchanges easy – for example by allowing rapid movement between two destinations, and providing quality public spaces in which people can meet and talk.

And the magic key to high agglomeration rates is mass transit:

  • Mass transit allows large numbers of people to be moved using very little land. If all those people I watched at the station were in cars, they would have needed a multi-lane highway rather than a narrow rail corridor for their journey.
  • Mass transit is easier to place underground – the most prosperous large cities all have underground metro systems. Even without an underground rail, you can (as Christchurch has) put light rail/trams through buildings or tunnels more readily than you can with a wide road full of noisy polluting traffic.
  • Mass transit can be integrated into high quality public spaces. No-one wants to stand chatting next to a busy road, but they can easily do so in a street that is only used by electric trams.
  • Because mass transit corridors are narrower and carry fewer vehicles, they are easier to cross than a multi-lane highway. And where pedestrians need to be kept out (e.g. with the heavy rail corridor), providing overbridges, subways or controlled crossings is easier because the corridor is narrower and the vehicles on it closely managed (KiwiRail knows where every train is, while NZTA does not even know how many vehicles are on the road system).
  • Mass transit is in itself a venue for social and economic exchange. You can run into a colleague as easily on a train as in a street, and carry out a conversation – not a good idea if you are both driving up the motorway. And mass transit encourages interactions between people who might not normally meet.

So if we want a vibrant and economically successful CBD, we need excellent mass transit, much less traffic, and high quality public spaces.



  1. […] This post was mentioned on Twitter by Tim Jones, Sustwelltrans. Sustwelltrans said: On our blog, Paula Warren talks about how mass transit systems lead to prosperous cities: #wellington […]

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