An active trip is the trip currently used by SityTrip when you add locations from a destination, a place sheet, or the map.
This allows you to quickly add places to the right trip, without having to select it each time.
To define a trip as active:
Once the trip is defined as active, the next locations added from SityTrip will be associated with this trip.
This allows you to plan several trips separately and choose at any time which one you wish to complete.