Carpool has goal reduction
Cost sharing
Carpooling usually means to divide the travel expenses equally between all the occupants of the vehicle (driver or passenger). The driver does not try to earn money, but to share with several people the cost of a trip he/she would do anyway. The expenses to be divided basically include the fuel and possible tolls. But if we include in the calculation the depreciation of the vehicle purchase and maintenance, insurance and taxes paid by the driver, we get a cost around $1/mile.
There are platforms that facilitate carpooling by connecting people seeking respectively passengers and drivers. Usually there is a fare set up by the car driver and accepted by passengers because they get an agreement before trip start.
The second generation of these platforms is designed to manage urban trips in real time, using the traveler's smartphones. They make possible to occupy the vehicle's empty seats on the fly, collecting and delivering passengers along its entire route (and not only at common points of origin and destination). This system automatically performs an equitable sharing of travel costs, allowing each passenger to reimburse the driver a fair share according to the benefit actually gained by the vehicle usage, proportional to the distance traveled by the passenger and the number of people that shared the car.