Link Trips

Link unlinked trip segments into complete journey records.

Detects mode changes and aggregates trip chains by validating spatial and temporal continuity across consecutive trips.

Algorithm

Phase 1: Link Trip IDs

1. Sort unlinked trips by person, day, and departure time
2. For each person-day sequence:
   • If previous trip's destination purpose is change_mode_enum, continue current linked trip
   • Validate spatial/temporal continuity:
     • Time gap between trips ≤ max_dwell_time minutes
     • Distance between previous destination and current origin ≤ dwell_buffer_distance meters
     • With split_on_occupancy, the reported party size is unchanged
   • Otherwise, start a new linked trip
3. Assign globally unique linked_trip_id: the day_id followed by a two-digit sequence number

Phase 2: Aggregate Linked Trips

1. Group unlinked trips by linked_trip_id
2. For each linked trip, aggregate:
   • Origin/Destination: First trip's origin, last trip's destination
   • Timing: First depart_time, last arrive_time
   • Distance: Sum of all trip distances
   • Duration: Sum of all trip durations (including dwell time)
   • Purposes: First origin purpose, last destination purpose
   • Mode Logic:
     • If any segment uses a transit mode → the mode of the longest-duration transit segment
     • Otherwise, the mode of the longest-duration segment
   • Transit Details: Count boarding/alighting, aggregate access/egress modes
   • Driver/Passenger: Aggregate from component trips

Notes

• Links trips when travelers make intermediate stops for mode changes or transfers
• Preserves full trip detail in unlinked_trips while creating journey-level linked_trips
• Transit detection ensures multi-modal journeys classified correctly
• Access/egress mode mapping converts trip modes to transit-specific codes
• Spatial/temporal thresholds prevent false linkages across separate journeys

Example

Example

- name: link_trips
  params:
    change_mode_enum: CHANGE_MODE
    transit_mode_enums: [FERRY, TRANSIT, LONG_DISTANCE]
    max_dwell_time: 180         # minutes
    dwell_buffer_distance: 100  # meters
    split_on_occupancy: false

Settings

Key	Type	Default	Meaning
change_mode_enum	text	required	Enum label indicating a mode change purpose.
transit_mode_enums	list	required	List of enum labels that count as transit modes.
max_dwell_time	number	120	Maximum time gap between trips to link them, in minutes (default: 120).
dwell_buffer_distance	number	100	Maximum spatial distance between trips to link, in meters (default: 100).
split_on_occupancy	true / false	required	Refuse to link two segments whose reported party size differs. A change of occupancy at a stop is evidence that somebody was picked up or dropped off, which makes the stop an activity rather than a transfer. Required, and deliberately without a default: either answer changes what a linked trip is, so the choice belongs to whoever configured the run rather than to this signature.

Code: processing.link_trips