Marchetti’s constant is the average time spent by a person for commuting each day. Its value is approximately one hour, or half an hour for a one-way trip. It is named after Italian physicist Cesare Marchetti, though Marchetti himself attributed the “one hour” finding to transportation analyst and engineer Yacov Zahavi.[1]

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.[1][2][3] In his 1934 book Technics and Civilization, Lewis Mumford attributes this observation to Bertrand Russell: