Marchetti's constant is the average time spent by a person for commuting each day, which is approximately one hour. The term is a misnomer, because Italian physicist Cesare Marchetti himself attributes the "one hour" finding to transportation analyst and engineer Yacov Zahavi.
Marchetti posits that although forms of urban planning and transport may change, and although some live in villages and others in cities, people gradually adjust their lives to their conditions (including location of their homes relative to their workplace) such that the average travel time stays approximately constant. Ever since Neolithic times, people have kept the average time spent per day for travel the same, even though the distance may increase due to the advancements in the means of transportation.
A related concept is that of Zahavi, who also noticed that people seem to have a constant "travel time budget", that is, "a stable daily amount of time that people make available for travel." David Metz, former chief scientist at the Department of Transport, UK, cites data of average travel time in Britain drawn from the British National Travel Survey in support of Marchetti's and Zahavi's conclusions. The work casts doubt on the contention that investment in infrastructure saves travel time. Instead, it appears from Metz's figures that people invest travel time saved in travelling a longer distance, a particular example of Jevons paradox described by the Lewis–Mogridge position.
- Marchetti, C., 1994: Anthropological Invariants in Travel Behavior, Technological Forecasting and Social Change , 47 :75–88, Internal Publication, International Institute for Applied Systems Analysis, Laxenburg, Austria
- Toward green mobility: the evolution of transport, Jesse H. Ausubel, Cesare Marchetti and Perrin Meyer, 1998 (accessed Nov 6, 2006); The Evolution of Transport, April/May 2001, Jesse H. Ausubel and Cesare Marchetti. Includes observations on historical cities.
- Metz, David, 2008: The Limits to Travel: How Far Will You Go?, 8, Earthscan, London
- The point is also made in a 2009 paper by Yves Crozet: 'Economic Development and the Role of Travel time: The key concept of accessibility' published in Commissioned Papers for the 4th International Future Urban Transport Conference of the Volvo Research and Educational Foundations, Gothenburg, Sweden, April 19–21, 2009.
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