A computer-controlled car that drives itself. Autonomous vehicles date back to the 1939 World's Fair in New York where the General Motor's exhibit predicted the development of driverless, radio-controlled electric cars. As TVs and modern appliances emerged in the U.S. in the 1950s, more images of driverless cars debuted. In the 1980s, experiments that detected the painted lines in the road were actually performed in the U.S. and Europe. In 2011, Nevada was the first state in the U.S. to legalize their use. Why? Accident avoidance is the major incentive because the car can respond faster than a human. In addition, people can arrive more relaxed after a long trip. Vehicles can travel closer together on the road, and computers can operate them more economically than people. The ultimate manifestation is the reduction of vehicles. For example, driverless taxis could replace a family's second car that sits idle most of the time. Of course, fewer cars overall has other implications (see computer ethics). DARPA Grand Challenges The Defense Advanced Research Projects Agency jump-started the driverless industry in the U.S. In 2004, DARPA offered monetary rewards for the winners of a 150-mile driverless vehicle race in the Mojave Desert in California. No vehicle completed the course, but 22 out of 23 finished the next race in 2005 with more curves and narrower roads. In 2007, six teams completed a 60-mile run through urban streets. LIDAR and Maps Driverless cars use lasers that scan the environment more than a million times per second (see LIDAR). Combined with digital GPS maps of the area, driverless cars detect white and yellow lines on the road as well as every stationary and moving object in their perimeter. Autonomous vehicles can drive themselves as long as a human driver can take control immediately when necessary. Google Self-Driving Car Project Although most automobile companies are in some stage of R&D for driverless cars, Google undertook its own project in 2009. Seven years later, Google spun off the technology into a new Alphabet division (see Waymo). Public Taxi Trials Have Begun In 2016, Uber and nuTonomy began driverless taxi trials in Pittsburgh and Singapore respectively. Engineers are present in the vehicles during these pilot programs to take over the wheel if necessary, but drivers do not talk to passengers in order to give them the full driverless experience. Also in September 2016, California sanctioned the trials of completely driverless cars (no steering wheel, brakes, etc.) in a Contra Costa County private business park. See Uber. The Transition to Driverless Cars Along with the huge technology challenge, state laws are being changed to allow them on the road. Whether autonomous vehicles become mainstream in a few years or decades away remains to be seen. However, in the meantime, accident prevention systems in regular cars are becoming much more advanced as a result of all the research (see adaptive cruise control). See semiautonomous vehicle, e-highway and automotive systems.