on the effective speed paradox

Bristol City Council have an excellent set of documents, produced by a chap from their Public Health department, Adrian Davis, reviewing the literature on walking and cycling. He makes one-page summaries that even councillors can understand. His review of the "effective speed paradox" (PDF) is a good one to refer people to when they claim that there's no point in providing for cycling in British towns and cities because people's lifestyles are too busy for such a slow form of transport.

In contrast, lower speeds in urban areas contribute to a higher quality of life in terms of the livability of public spaces, including lower crime rates and higher levels of social interactions between people. ???Streets with low traffic speeds and volumes have been found to have more indicators of a better quality of life???more street activity, more signs of street care (e.g. flower boxes) and more open windows???. The effective speed concept suggests that lower speeds ultimately save time as retention of high density enables people to access services and facilities by sustainable modes not possible even by car with low density land use planning. This is a paradox of the effective speed concept.

The original paper is archived on PMC and full of quotable bits and pieces:

Speed Kills: The Complex Links Between Transport, Lack of Time and Urban Health
Paul Joseph Tranter, PhD. J Urban Health. 2010 March; 87(2): 155???166.
PMCID: PMC2845829

In addition to these impacts, a heavy reliance on cars as a supposedly ???fast??? mode of transport consumes more time and money than a reliance on supposedly slower modes of transport (walking, cycling and public transport). Lack of time is a major reason why people do not engage in healthy behaviours. Using the concept of ???effective speed???, this paper demonstrates that any attempt to ???save time??? through increasing the speed of motorists is ultimately futile. Paradoxically, if planners wish to provide urban residents with more time for healthy behaviours (such as exercise and preparing healthy food), then, support for the ???slower??? active modes of transport should be encouraged.

One of the best examples is Graz, Austria, which adopted a 30-km/h limit throughout most of the city in the early 1990s, reducing serious casualties by over 25% as well as significantly reducing noise and air pollution. At the time the lower speed limits were introduced, less than 50% of residents supported the initiative but, after their benefits became evident, the support grew to 80%.

It might be expected that cities with higher traffic speeds would have lower daily Travel Time Budgets (TTBs; time spent on travel each day). In fact, the opposite is true. Western European cities have TTBs of about 43??min and distance travelled of about 21??km. In contrast, North American cities have TTBs of around 55??min with 40??km distances. The increased speed is not used to save time but to cover more distance. Consequently, as the city expands (or as shops, jobs and services become more dispersed), even more speed is needed to overcome the increased distances. However, the increases in speed do not fully compensate for the increasing distances, and hence low density cities pay for their dispersion with longer travel times.


as well as considering the time spent during each trip, it is also necessary to consider the time associated with every other activity necessitated by that mode. For most car drivers, the most time-consuming task associated with their car is the time spent at work to earn the money to pay for all the costs associated with the car. Note that these costs are simply the direct costs associated with car driving, but there are also indirect or external costs that are shared amongst the whole society (both now and in the future). These include the health and environmental costs associated with car driving… When these external costs are considered, we can refer to ???social effective speed???.

Nothing particularly new, of course — Ivan Illich wrote something similar in Energy and Equity in 1974, as quoted on the opening pages of Lynn Sloman's Car Sick.

The typical American male devotes more than 1,600 hours a year to his car. He sits in it while it goes and while it stands idling. He parks it and searches for it. He earns the money to put down on it and to meet the monthly instalments. He works to pay for petrol, tolls, insurance, taxes and tickets. He spends four of his sixteen waking hours on the road or gathering his resources for it. And this figure does not take into account the time consumed by other activities dictated by transport: time spent in hospitals, traffic courts and garages; time spent watching automobile commercials or attending consumer education meetings to improve the quality of the next buy. The model American puts in 1,600 hours to get 7,500 miles: less than five miles per hour. In countries deprived of a transportation industry, people manage to do the same, walking wherever they want to go, and they allocate only three to eight per cent of their society's time budget to traffic, instead of 28 per cent.

Not to mention the number of years that not cycling and walking takes off your life expectancy.
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