Catchment Area - The Sam's Club Effect

Assuming a constant allowable travel time, the catchment area of a retail outlet, etc. goes up geometrically with increased speed of travel.

However, if you can assume with less frequent visits (i.e. larger quantities with each trip,) the allowable travel time goes up, then the catchment area increases still further with the square of the distance travelled. Hence, the Sam's Club Effect.

[Catchment Area = Pi X (Allowable Travel Time X Speed of Travel) Squared]

Compare: The March away from Density