Marchetti's constant

Who is Marchetti's constant?

Marchetti's constant is a term for the average amount of time spent commuting each day, which is approximately one hour. Developed by Venetian physicist Cesare Marchetti, it 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 such that the average travel time stays approximately constant. Even since Neolithic times, people have kept the time at which they travel per day the same, even though the distance may increase.

Activist, consultant and author Peter Newman often makes reference to Marchetti's Constant in his arguments for sustainable urban planning and transport.

A related concept is that of Yakov Zahavi, who also noticed that people seem to have a constant 'travel time budget'. Zahavi's work is cited by David Metz in his book 'The Limits to Travel' published by Earthscan, London p. 8. Metz refers to the travel time budget as 'a stable daily amount of time that people make available for travel'. Metz cites data of average travel time in Britain drawn from the British National Travel Survey in support of Marchetti's and Zahavi's conclusions.