Friction of distance

The concept of friction of distance is based on the notion that distance usually requires some amount of effort (energy) and/or money to overcome. Because of this "friction", spatial interactions, especially transport and the particular case of human migration, will tend to take place more often over shorter distances; amount and intensity of interaction will decay with distance. Even though no physical friction is involved, price and effort are metaphorically assumed to correspond to forces counteracting transport movements.