In telecommunication, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a portmanteau of transmitter and responder. It is variously abbreviated as XPDR, XPNDR, TPDR or TP.
Personal rapid transit (PRT), also referred to as podcars or guided/railed taxis, is a public transport mode featuring small automated vehicles operating on a network of specially built guideways. PRT is a type of automated guideway transit (AGT), a class of system which also includes larger vehicles all the way to small subway systems. In terms of routing, it tends towards personal public transport systems.
An intelligent transportation system (ITS) is an advanced application which aims to provide innovative services relating to different modes of transport and traffic management and enable users to be better informed and make safer, more coordinated, and 'smarter' use of transport networks.
In transportation, platooning or flocking is a method for driving a group of vehicles together. It is meant to increase the capacity of roads via an automated highway system.
A self-driving car, also known as an autonomous vehicle, driverless car, or robo-car, is a vehicle that is capable of sensing its environment and moving safely with little or no human input.
Road traffic safety refers to the methods and measures used to prevent road users from being killed or seriously injured. Typical road users include pedestrians, cyclists, motorists, vehicle passengers, horse riders, and passengers of on-road public transport.
Speed bumps are the common name for a class of traffic calming devices that use vertical deflection to slow motor-vehicle traffic in order to improve safety conditions. Variations include the speed hump, speed cushion, and speed table.
Tailgating is when a driver drives behind another vehicle while not leaving sufficient distance to stop without causing a collision if the vehicle in front stops suddenly.
Advanced driver-assistance systems (ADAS) are electronic systems that assist drivers in driving and parking functions. Through a safe human-machine interface, ADAS increase car and road safety. ADAS systems use automated technology, such as sensors and cameras, to detect nearby obstacles or driver errors, and respond accordingly.
The two-second rule is a rule of thumb by which a driver may maintain a safe trailing distance at any speed. The rule is that a driver should ideally stay at least two seconds behind any vehicle that is directly in front of his or her vehicle. It is intended for automobiles, although its general principle applies to other types of vehicles. Some areas recommend a three-second rule instead of a two-second rule to give an additional buffer.
Automatic number-plate recognition is a technology that uses optical character recognition on images to read vehicle registration plates to create vehicle location data. It can use existing closed-circuit television, road-rule enforcement cameras, or cameras specifically designed for the task. ANPR is used by police forces around the world for law enforcement purposes, including to check if a vehicle is registered or licensed. It is also used for electronic toll collection on pay-per-use roads and as a method of cataloguing the movements of traffic, for example by highways agencies.
Dooring is the act of opening a motor vehicle door into the path of another road user. Dooring can happen when a driver has parked or stopped to exit their vehicle, or when passengers egress from cars, taxis and rideshares into the path of a cyclist in an adjacent travel lane. The width of the door zone in which this can happen varies, depending upon the model of car one is passing. The zone can be almost zero for a vehicle with sliding or gull-wing doors or much larger for a truck. In many cities across the globe, doorings are among the most common and injurious bike-vehicle incidents. Any passing vehicle may also strike and damage a negligently opened or left open door, or injure or kill the exiting motorist or passenger.
Vehicular automation involves the use of mechatronics, artificial intelligence, and multi-agent system to assist a vehicle's operator. These features and the vehicles employing them may be labeled as intelligent or smart. A vehicle using automation for difficult tasks, especially navigation, may be referred to as semi-autonomous. A vehicle relying solely on automation is consequently referred to as robotic or autonomous. After the invention of the integrated circuit, the sophistication of automation technology increased. Manufacturers and researchers subsequently added a variety of automated functions to automobiles and other vehicles. The technology involved in implementing autonomous vehicles is very expansive, ranging from technological improvements on the vehicle itself to the environment and objects around the vehicle. As the use of automated vehicles increases, they are becoming more influential in human lives. Although automated vehicles bring various benefits, it also comes with various concerns. Also, there are still technology challenges that autonomous vehicles seek to make a breakthrough in order to make it robust and scalable.
Headway is the distance between vehicles in a transit system measured in time or space. The minimum headway is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise definition varies depending on the application, but it is most commonly measured as the distance from the tip of one vehicle to the tip of the next one behind it. It can be expressed as the distance between vehicles, or as time it will take for the trailing vehicle to cover that distance. A "shorter" headway signifies closer spacing between the vehicles. Airplanes operate with headways measured in hours or days, freight trains and commuter rail systems might have headways measured in parts of an hour, metro and light rail systems operate with headways on the order of 90 seconds to 5 minutes, and vehicles on a freeway can have as little as 2 seconds headway between them.
A collision avoidance system (CAS), also known as a pre-crash system, forward collision warning system, or collision mitigation system, is a motorcar safety system designed to prevent or reduce the severity of a collision. In its basic form, a forward collision warning system monitors a vehicle's speed, the speed of the vehicle in front of it, and the distance between the vehicles, so that it can provide a warning to the driver if the vehicles get too close, potentially helping to avoid a crash. Various technologies and sensors that are used include radar (all-weather) and sometimes laser (LIDAR) and cameras to detect an imminent crash. GPS sensors can detect fixed dangers such as approaching stop signs through a location database. Pedestrian detection can also be a feature of these types of systems.
In legal terminology, the assured clear distance ahead (ACDA) is the distance ahead of any terrestrial locomotive device such as a land vehicle, typically an automobile, or watercraft, within which they should be able to bring the device to a halt. It is one of the most fundamental principles governing ordinary care and the duty of care for all methods of conveyance, and is frequently used to determine if a driver is in proper control and is a nearly universally implicit consideration in vehicular accident liability. The rule is a precautionary trivial burden required to avert the great probable gravity of precious life loss and momentous damage. Satisfying the ACDA rule is necessary but not sufficient to comply with the more generalized basic speed law, and accordingly, it may be used as both a layman's criterion and judicial test for courts to use in determining if a particular speed is negligent, but not to prove it is safe. As a spatial standard of care, it also serves as required explicit and fair notice of prohibited conduct so unsafe speed laws are not void for vagueness. The concept has transcended into accident reconstruction and engineering.
Experiments have been conducted on self-driving cars since at least the 1920s; promising trials took place in the 1950s and work has proceeded since then. The first self-sufficient and truly autonomous cars appeared in the 1980s, with Carnegie Mellon University's Navlab and ALV projects in 1984 and Mercedes-Benz and Bundeswehr University Munich's Eureka Prometheus Project in 1987. Since then, numerous major companies and research organizations have developed working autonomous vehicles including Mercedes-Benz, General Motors, Continental Automotive Systems, Autoliv Inc., Bosch, Nissan, Toyota, Audi, Volvo, Vislab from University of Parma, Oxford University and Google. In July 2013, Vislab demonstrated BRAiVE, a vehicle that moved autonomously on a mixed traffic route open to public traffic.
A protected intersection is an at-grade road junction in which cyclists and pedestrians are separated from cars. Vehicles turning right are separated from crossing cyclists and pedestrians by a buffer, providing increased reaction times and visibility. Drivers looking to turn right have better visibility of cyclists and pedestrians as they can look to the side for conflicts instead of over their shoulders. At unsignalized intersections, it is practice to have one car length of space between the cycleway and roadway, so that cars exiting the minor street have an area to pull forward and wait for a gap in traffic, without becoming distracted by potential simultaneous conflicts along the cyclepath.
The death of Elaine Herzberg was the first recorded case of a pedestrian fatality involving a self-driving car, after a collision that occurred late in the evening of March 18, 2018. Herzberg was pushing a bicycle across a four-lane road in Tempe, Arizona, United States, when she was struck by an Uber test vehicle, which was operating in self-drive mode with a human safety backup driver sitting in the driving seat. Herzberg was taken to the local hospital where she died of her injuries.
