Carpool Programs, Ridesharing and

Ridesharing has long been viewed as an approach to address problems of traffic congestion, carbon emissions, and fossil fuel dependence. The objective of ridesharing is to fill empty vehicle seats by matching riders with drivers going in a similar direction, employing vehicle occupancy potential to reduce the number of vehicles on the roadways. Ridesharing is largely realized through carpooling and vanpooling, the grouping of travelers in a private automobile or van, respectively. Ridesharing also includes more unique forms, such as casual carpooling (also known as “slugging”). North American ridesharing has a 70-year history, which began with carpooling programs during World War II and has evolved through five phases until today. Ridesharing's modal share has declined since the 1970s, when 20.4 percent of American workers commuted to work by carpool. Despite this drop, it remains the second-largest travel mode in the United States, at 10.2 percent as of 2011.

In traditional definitions, ridesharing differs from for-profit commercial transportation (for example, taxicabs, limousines) in its financial motivation. When a ridesharing payment is collected, it partially covers the driver's cost; it is not intended to result in a financial gain. Moreover, the driver has a common origin and/or destination with the passengers.

Because ridesharing reduces the number of automobiles needed by travelers, it claims numerous societal benefits, including reduced emissions, traffic congestion, and parking infrastructure demand. However, the magnitude of such benefits is unclear. On an individual level, the benefits are more tangible. Carpool and vanpool participants experience cost savings due to shared travel costs, travel-time savings through the use of high occupancy vehicle (HOV) lanes, and reduced commute stress, particularly for those with longer commute distances. In addition, they often have access to preferential parking and additional incentives.

Despite its many benefits, there are numerous behavioral barriers to increased ridesharing use. Individuals often see the attractiveness of carpooling but are disinclined to sacrifice the flexibility and convenience of the private automobile. Moreover, psychological factors, such as the desire for personal [Page 357]space and time and an aversion to social situations, can impact ridesharing adoption. Personal security is also a concern when sharing a ride with strangers, although this is a perceived risk. Carpool programs over the years have attempted to address these barriers using incentives and emerging technology.