Peer-to-peer ridesharing can be divided along the spectrum from commercial, for-fee transportation network companies (TNC) to for-profit ridesharing services to informal nonprofit peer-to-peer carpooling arrangements. The term transportation network company comes from a 2013 California Public Utilities Commission ruling that decided to make the TNC revenue model legal. Almost all modern peer-to-peer ridesharing schemes rely on web application and mobile app technology.
In the early 2010s, several transportation network companies were introduced. These were advertised as ridesharing, but dispatch drivers in a fashion similar to a taxi service, where they do not share a destination with passengers. The first such service to appear on the market was the San Francisco-based company Sidecar (launched in 2011). Transportation experts have called these services "ridesourcing" to clarify that drivers do not share a destination with their passengers; the app simply outsources rides to commercial drivers. Despite multiple efforts to re-name the category, it still is commonly referred to as, "ridesharing".
Real-time ridesharing (also known as instant ridesharing, dynamic ridesharing, ad-hoc ridesharing, on-demand ridesharing, and dynamic carpooling) is a service that arranges one-time shared rides on very short notice. This type of carpooling generally makes use of three recent technological advances:
These elements are coordinated through a network service, which can instantaneously handle the driver payments and match rides using an optimization algorithm.
Like carpooling, real-time ridesharing is promoted as a way to better utilize the empty seats in most passenger cars, thus lowering fuel usage and transport costs. It can serve areas not covered by a public transit system and act as a transit feeder service. Ridesharing is also capable of serving one-time trips, not only recurrent commute trips or scheduled trips.
Real-time ridesharing is especially suitable for daily commuting compared to driving alone. Because such trips tend to happen at peak travel times, when traffic jams cause cars to pollute an 80% more, additional benefits for the urban environment and climate change mitigation are expected by a reduction in the number of cars riding daily by the cities with a single occupant, and their related CO2 and NOx emissions.
A 2010 survey at the University of California, Berkeley found 20% of respondents are willing to use real-time ridesharing at least once a week; and real-time ridesharing was more popular among current drive-alone commuters (30%) than transit or non-motorized commuters. The top obstacles to using real-time ridesharing were short trip lengths and the added time of ride logistics.
Early real-time ridesharing projects began in the 1990s, but they faced obstacles such as the need to develop a user network and a convenient means of communication. Gradually the means of arranging the ride shifted from telephone to internet, email, and smartphone; and user networks were developed around major employers and universities. As of 2006, the goal of taxi-like responsiveness still generally eluded the industry; "next day" responsiveness was considered the state of the art. More recently taxi-sharing systems that accept taxi passengers’ real-time ride requests via smartphones have been proposed and studied.
A number of technology companies based in San Francisco premiered apps for real-time ridesharing (as well as ride-hailing where the driver does not share a destination with passengers) around 2012. However, in the fall of 2012, the California Public Utilities Commission issued a cease and desist letter to rideshare companies Lyft, Uber, Wingz, and Sidecar, and fined each $20,000. In 2013 an agreement was reached reversing those actions, creating a new category of service called "Transportation Network Companies" to cover both real-time and scheduled ride-sharing companies. Transportation Network Companies have faced regulatory opposition in many other cities, including Los Angeles, Chicago, New York City, and Washington, D.C.
Two dynamic ridesharing pilots in Norway received government funds from Transnova in 2011. One pilot in Bergen had 31 passengers in private cars during one day. Thirty-nine users acted as drivers or passengers between June 30 and September 15 with four ridesharing episodes or more. The phone apps that was used was Avego Driver and HentMEG.no cell client, a prototype developed for the NPRA of Norway. The other pilot is run by the company Sharepool.
Some more advanced real-time ridesharing features have been proposed but not implemented. For example, longer trips might be facilitated using "multihop" matches in which passengers change cars to reach their final destination.
Some jurisdictions have considered and/or implemented caps on the number of drivers who can work for ride-sharing companies. A 2018 survey of leading economists showed that most of the economists believed that such caps would have adverse effects, with a near-consensus noting that congestion pricing would be a better way to reduce congestion than ride-sharing caps.
Several studies and analyses of ridesharing apps (such as Uber and Lyft) have found that they reduce DUI accidents and fatalities. One study concluded that Uber had no impact on DUI accidents and fatalities.
Some studies suggest that ridesharing apps increase overall traffic accidents and fatalities, possibly because rideshare drivers are distracted by their mobile devices or have to drive erratically at times to pick up customers.
One study concluded that ridesharing apps increase overall traffic and gas consumption and cause greater traffic delays.