Accesibilidad en las ciudades

 

 

 

http://discoveringurbanism.blogspot.mx/2010/02/from-mobility-to-accessibility.HTML

 

From a mobility to an accessibility orientation

Over at the Planetizen Interchange blog, a fascinating debate has been brewing over the fundamental purpose of transportation. Todd Litman, Sam Staley, Michael Lewyn and a handful of commenters are involved. When debating transportation, we often jump right to the question of automobile vs. transit, but the more interesting dividing line lies beneath whatever technological tool we prefer. The tool of choice will arise inevitably out of what we intend to do with the system.

A mobility-oriented analysis, the conventional approach taken by transportation planners throughout the 20th century, is represented by Sam Staley. In his aptly titled book Mobility First, he defines this simply as:

"The ability to travel where you want when you want"

Working toward higher levels of mobility, for Staley, is a necessary condition for economic development and the maintenance of a high quality of life for Americans. This requires a combination of building sufficient capacity to meet travel demand and the efficient use of the capacity. For capacity, Staley calls for an aggressive government road-building regime, with thousands of miles of tunnels and multi-level expressways. For efficiency, he proposes a pricing system based on peak usage and levels of congestion.

In a mobility-oriented analysis, success is measured in terms of vehicle miles traveled - the more movement, the better. This position naturally leads Staley to hold the private automobile up as the ultimate mode of travel:

"Cars provide the automobility people want, fusing speed, flexibility, and adaptability into one travel technology. In a service-based economy faced with global competition, cars provide the most efficient, effective, and productive transportation alternative."

An accessibility-oriented analysis shifts the primary goal up one level. Instead of simply attempting to maximize the total amount of movement, this approach places primacy on the ability to reach a chosen destination. Todd Litman represented this side of the debate, and he has covered it more thoroughly here. His definition of accessibility:

"The ease of reaching goods, services, activities and destinations (together called opportunities). It can be defined as the potential for interaction and exchange."

It's a subtle difference with major implications. I've assembled a simplified flow chart to represent what I take to be the essential contours of an accessibility approach:
(In reality, there are overlaps and feedback loops between these categories. This just shows a hierarchy of goals.)

In this approach, mobility is not an end itself but a means to the end of improving access to destinations. Granted there are a few exceptions, such as joyriding, walking the dog around the block and other recreational activities, but, for the most part, users of the transportation system are concerned with reaching their destination. This interaction is also what truly drives economic and social health. Mobility no longer holds the trump card in an accessibility paradigm, but it must compete with land use arrangements and other alternatives to movement in a cost-benefit analysis. Litman again:

"Just as automobiles are machines that provide mobility, urban environments - villages, towns and cities - can be thought of as machines that provide accessibility by minimizing the distance among people and their desired goods, service and activities (shops, schools, jobs, neighbors, etc.)."

When mobility was considered the only game in town, the costs, however large, had to be shrugged off as a necessary evil. On top of all of the money poured into car-based infrastructure already, Staley claims "we probably need to spend at least a trillion dollars more on transportation over the next decade than we expect in revenues if we want to keep up with growth in travel and goods movement." (my italics). This is a significant chunk of the U.S. GDP, and it doesn't even count the costs of manufacturing and fueling the vehicles. He would like to slowly shift this immense burden from government to private citizens, which will surely add to the growing expense American households are already pouring into transportation.

Of course, there are the environmental costs, social equity costs and the costs in human lives. Roadway fatalities per capita have remained remarkably steady since 1960, even as medical care and general quality of life have improved significantly. Even in the most efficient system, there are the costs in the time it takes to move over longer distances. All of this needs to be figured into the equation.

There are immense benefits to mobility too, in all of its forms. None of this suggests that we can grind the world to a halt and still maintain the economic vitality we enjoy. It, however, does suggest a more holistic strategy - a full toolbox to respond to a broader challenge.