Monday, 30 March 2009

Travel Patterns Over Generations

Over generations and time the travel behaviour has changed, especially in term of distance. From looking at travel patterns on a city scale for this bog post we are looking at a global level. It has become normal to travel around the world and any location on this planet is now to be reached in a day or two.
Within only four generations, or one century, the covered land by life time tracks has grown from a regional are to a national to a continental and finally to a global area.
Ways in which travel patterns have changed for the host population over recent generations have been shown in an interesting way by the distinguished epidemiologist, David Bradley6, when he was at the London School of Hygiene and Tropical Medicine. Bradley compared the travel patterns of his great-grandfather, his grandfather, his father and himself (see Figure 2). The life-time travel track of his great-grandfather around a village in Northamptonshire could be contained within a square of only 40 km side. His grandfather’s map was still limited to southern England, but it now ranged as far as London and could be contained within a square of 400 km side. If we compare these maps with those of Bradley’s father (who traveled widely in Europe) and Bradley’s own sphere of travel, which is worldwide, then the enclosing square has to be widened to sides of 4000 km and 40,000 km, respectively. In broad terms, the spatial range of travel has increased 10-fold in each generation so that Bradley’s own range is 1000 times wider than that of his great-grandfather. (British Medical Bulletin 69:87-99 (2004))

Image taken from British Medical Journal

Bradley’s record of increasing travel over four male generations of the same family6. (A) Great-grandfather. (B) Grandfather. (C) Father. (D) Son. Each map shows in a simplified manner the individual’s ‘life-time tracks’ in a widening spatial context, with the linear scale increasing by a factor of 10 between each generation.

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