Carpooling is the practice of sharing car journeys with others so that more than one person travels in a car, reducing the need for others to drive to a location themselves. Carpooling is commonly used for commuting, but it is also increasingly popular for longer one-off journeys. The formality and regularity of arrangements vary between schemes and journeys. Carpooling can be arranged for the whole length of a journey, or passengers can join for parts of the journey and give a contribution based on the distance they travel. There are platforms that facilitate carpooling by connecting people seeking passengers and drivers. Carpooling can take different forms, such as:

• Flexible carpooling: This expands the idea of ad hoc carpooling by designating formal locations for travelers to join carpools.
• Slugging: This is a form of ad hoc, informal carpooling between strangers. No money changes hands, but a mutual benefit still exists between the driver and passenger(s) making the practice worthwhile.

Benefits of carpooling include:

• Shared costs: Carpooling reduces the cost of travel for each person involved.
• Reduced carbon footprint: Carpooling reduces the number of individual cars on the road, which helps to reduce carbon emissions.
• Easing road congestion: Carpooling and bikes are two effective ways of reducing car use. The more people do it, the less congested our city roads will be.

Carpooling has evolved over time, and it has played a critical role in planning city infrastructure and tackling avoidable congestion costs. The concept of carpooling first arose as an economic necessity back in World War II when the American government promoted it as a method of rationing fuel. Nowadays, carpooling has become increasingly popular due to growing populations, infrastructure needs, and congestion.