Making a journey between two zones on a transport network depends on the following three fundamental elements (El-Geneidy and Levinson 2006):

The potential of the origin zone to generate the journey. This variable will further depend on the number of inhabitants in the zone, the population’s level of motorisation and their standard of living along with other factors.

The capacity of the destination zone to attract a trip. The attraction depends on the population, the number of commercial premises, the number of jobs and other facilities present in the destination zone.

The difficulty in travelling between the origin and destination zones. In order for this to affect the journey, the effect of this cost has to be lower than the destination’s power of attraction.