Following somewhat from the discussion on slow transit and travel times, I coincidentally happened to read a paper today that sheds some light onto the ‘magic one hour limit’. This idea that people are willing to travel up to an hour each way to work is more or less considered a fact in transport planning literature, but why is this so, and has it always been that way?
The paper I read was entitled “Anthropological Invariants in Travel Behaviour”, written by an anthropologist named Marchetti almost two decades ago. Marchetti claims that travel patterns are determined by basic animal instincts, innate behaviours of survival and prosperity-seeking that have remained constant across aeons of technological development.
According to him there are two competing instincts that influence travel behaviours: the first is the instinct for territorial animals such as humans to strive to increase their territory. This in order to maximise access to resources and expand the powerbase, a strategy that promotes long term survival and prosperity. The second instinct is the drive to limit exposure to hostile forces and remain within easy reach of a defensible ‘nest’ such as a cave, or in modern terms, a house. This strategy promotes short term survival and the maintenance of existing resources.
So what does this mean? Well according to Marchetti the trade off between these two instincts results in people feeling the need to travel on a daily basis, but not wanting to stray more than one hour travel time from home. So there we have it: commuting an hour each day to hunt, gather or otherwise work for a living is a basic survival instinct we’ve had since we were cavemen.
This concept suggests that settlements will naturally spread up to one hours travel across, much more than that and our animal instincts fall out of balance. People can typically walk around 5km per hour across good terrain, so back in the days when travel was almost exclusively by foot functional cities could only be approximately 5km across. Marchetti claims this is exactly how big they got, apparently ancient walled cities were almost all 5km across while the core of the modern day walking city of Venice is the same size. With the introduction of horse travel, railways, cars and then airplanes, the distance one can travel in an hour has successively increased. With the car and motorways people can live their lives in a city a hundred kilometres across, as we see in Auckland and other places today. For people that commute via air shuttle or high speed rail, their ‘home town’ becomes three or four hundred kilometres across. Indeed the Paris commuter belt now extends from the Belgian border half way to the Pyrenees thanks to the TGV network.
One interesting thing to consider is that when travel distance increases linearly, the area accessible increases exponentially. For example, the 5km wide one-hour-walking city covers around 20km2 (about the area from Ponsonby to Parnell) the 100km wide one-hour-driving city covers 7,800km2 (about the size of the greater Auckland region) while the 300km wide one-hour-by-high-speed-rail city could cover a staggering 70,600km2 (about the size of Ireland!).
The one-hour city by foot… and by car.
This leads to the question, do we need to live our day to day lives over such a great distance, what are the pros and cons of having such a great area within one hours’ travel?
The arguments against are much the same as the arguments against sprawl. Things like the waste of energy and resources spent travelling such great distances, the huge expense on infrastructure and the consumption of natural environments or productive rural land for urban uses. The arguments for are largely from the economic sector, suggestions that a city covering a larger area can have a much larger population as part of the single economic unit. This give people greater access to jobs and services, while conversely businesses have a wider pool of labour from which to select the most appropriate staff. Furthermore there are economies of scale to be had with large cities giving them a competitive edge in the global marketplace, and wider cities mean more people without super cramped conditions.
Marchetti raises the prospect that once 500km/h+ maglev technologies are deployed in regular usage conurbations will become immense, with places like the Tokyo-Osaka corridor functioning as a single city of over 100 million people. The prospects of a city that size are both terrifying and amazing at the same time.