Permeability is the number of alternative routes from one point to another and, therefore, having ease of access and connectivity to a surrounding environment. Filtered permeability of an area differentiates between road user categories.
“Filtered permeability is the principle followed in European towns and cities most successful in restraining car use. It means separating the sustainable modes from private motor traffic in order to give them an advantage in terms of speed, distance and convenience. There are many ways in which this can be done: separate cycle and walk ways, bus lanes, bus gates, bridges or tunnels solely for sustainable modes.” See:
Sometimes also differentiated permeability is organized for distinguished car users, e.g. resident vs. non-resident, HGV vs. LCV and passenger cars. Within ReVeAL we consider filtered permeability obtained by means of UVAR.