The definition of carpooling seems simple but packs a big punch. Carpooling is when two or more people -- typically from different households -- share an automobile journey together. Usually people arrange carpools in order to save money, protect the environment by burning less gasoline or to enjoy each other's company.
Carpooling can be regular and formalized, such as every workday or every Thursday. Or it could be arranged for especially long or unusual car trips. The majority of carpools for work commutes are family members driving together. However, many large cities offer carpool pickup locations where drivers can pick up a stranger to drive in or out of the urban area. Usually these correlate with carpool lanes on the highways that let cars with a specific number of people -- often set at two or three or more -- to give drivers an incentive to pick up passengers.
Cities with worse traffic, longer commutes and longer rush hour times often have more people who want to carpool. In areas where you find "extreme commuters" traveling an hour or more to work every day, there is even more demand for carpooling. Carpoolers can find a ride share through the Internet or workplace carpool postings. The government and many employers encourage carpools as a convenience for workers and to ease congestion on the roads.
Sometimes, the passengers will offer to pay for gas or tolls as a thank you to the driver. On very long cross-country drives, they may take a turn manning the steering wheel. Of course, if you accept a carpool, you may need to compromise on your specific work hours in order to make a carpool happen.