Tour-based models arrange travel into units called tours. Tours are travel events that start at one location and return to that same location. For example, when a person travels to work and returns home, this a home-based work tour. A tour can have two or more trips.
Activity-based models are tour-based, but a model does not have to be activity-based to be tour-based.
A sub-tour is a tour that occurs temporally within another tour. For example, if a worker goes from home to work, and goes from work to a restaurant back to work, and then goes back home, this activity chain contains one sub-tour.
Each tour is divided into two 'half-tours'- one from the primary origin to the primary destination, and one from the primary destination back to the origin.
The half-tour leaving from the primary origin is called 'outbound. The half-tour leaving from primary destination is called 'inbound'.
# Intermediate stops
A tour may have zero or many 'intermediate stops'. An intermediate stop occurs when a person participates in an activity at a location that is not the tour origin or destination. For example, if a person goes from home to work and picks up coffee along the way, the place where the person got the coffee is an intermediate stop.