The City Steals Time and Offers Speed: Mobility Versus Accessibility

The city steals time and offers speed when it confuses mobility, the ability to move, with accessibility, the ability to reach what you need. Two people leave home at the same hour and travel for the same forty-five minutes: one lives downtown and can reach hundreds of thousands of jobs, three hospitals and dozens of schools; the other lives on the edge and reaches an industrial estate, one overloaded clinic and little else. Neither moves faster, no transport statistic tells them apart, and yet they live in different cities. Mobility is measured in speed, distance and vehicles per hour; accessibility in opportunities reachable within a reasonable time. One indicator rewards movement, the other rewards nearness, and a city can improve the first while worsening the second.

Induced distance: why wider roads do not save time

The mechanism is induced distance. When a motorway is widened, the trip gets shorter for a while, but a faster journey makes living and building further out worthwhile: scattered estates, isolated shopping centres and logistics parks appear on the fringe, and distance grows until it swallows the time saved. Studies of induced demand are consistent: adding road capacity generates extra traffic in almost equal proportion and congestion returns within a few years, as the widening of Houston's Katy Freeway to more than twenty lanes showed when travel times worsened again. This is not a failure of execution but the normal behaviour of the system. Infrastructure does not hand out time; it redistributes distance.

The travel time budget: Zahavi, Marchetti and Metz

The uncomfortable finding is the travel time budget. The physicist Cesare Marchetti popularised in 1994 an observation the engineer Yacov Zahavi had made in the 1970s: the average time a person spends travelling each day stays remarkably stable at around one hour, regardless of era or technology. We swapped the horse for the tram and the tram for the car, and we still spend the same; what changes is the distance covered. The transport researcher David Metz tested this against national travel surveys and concluded that investing in speed does not save time but stretches journeys. Promising minutes through public works promises something the territory hands back as kilometres.

Who pays first: peripheries, care trips and the accessibility indicator

Who pays first is clear. In many Latin American capitals, low-income households spend more than twice as long on the daily commute as wealthy households, leaving in darkness and returning in darkness, because cheap land lies far from jobs and services. Inside the home, care trips, taking someone to school, to the doctor or to the shops, are short, chained and mostly made by women, and almost no transport model counts them properly. The planner Robert Cervero has argued for years that transport projects should be judged by the accessibility they create rather than by the minutes they promise to save, and that change of indicator is political, because measuring accessibility forces one to look at land, not only asphalt: where the jobs and hospitals are, how dense each neighbourhood is and what uses the plan allows.

The 15-minute city and its limits: scale and land prices

Very often the best transport policy is not a new road but a well-placed school, a health centre within walking distance or simply permitting housing where services already exist; the 15-minute city popularised by Carlos Moreno is a public version of this old idea, bringing things closer instead of moving faster. The counterargument deserves a fair hearing. Not every service can be replicated in every neighbourhood, because a specialised hospital, a university or a skilled job needs metropolitan scale, and a badly applied language of closeness can lock poorer people inside their district with reduced versions of everything while the wealthy still reach the whole city. Accessibility is also capitalised into land prices: when a neighbourhood becomes highly accessible, rents rise and push out the people it was meant to help.

A more precise position can then be defended: accessibility without land redistribution is a slogan, and mobility without accessibility is a machine for producing distance. Speed, well distributed, remains an instrument of equality, and the problem is not moving fast but who gets to. The city that steals time is the one that measures itself in vehicles per hour and builds outward; the one that gives it back measures how many opportunities each resident can reach in forty-five minutes, plans land and transport together and protects those who live near the opportunities from being priced out of them.