Linked from
The 11 pages that link to Carpool, each with the reason it gives.
AutomobileRelated: It increases the number of passengers carried per automobile trip.
Passenger carRelated: It increases the number of passengers carried per vehicle trip.
Private transportRelated: Sharing a private vehicle can reduce the number of cars used for a trip.
Shared transportRelated: It fills spare seats in privately owned cars for a common trip.