Over the last few years automotive manufacturers have been introducing sophisticated vehicle control technologies to improve safety, fuel efficiency and comfort level of drivers, amongst other things. These new technologies are sometimes called Advanced Driver Assistance Systems (ADAS). These systems use sensor technology, including automotive radar, that has been developed specifically for use in motor vehicles (See Warning and Control). They have a positive effect on safety and traffic management by helping drivers to maintain a safe speed and distance, keep within the running lane and avoid unsafe overtaking manoeuvres. Benefits can be further magnified if individual vehicles communicate continuously with each other or with the road infrastructure – so-called ‘connected’ vehicles (See Connected Vehicles).
Examples of longitudinal vehicle control are Adaptive Cruise Control (ACC) and Co-operative Adaptive Cruise Control (CACC). ACC is designed so that a car automatically maintains a safe distance from the vehicle ahead in terms of distance or time headway, as programmed by the driver. The driver specifies the maximum speed (as with normal cruise control) and the follow distance. An on-board radar sensor locks onto the vehicle ahead and the vehicle control system maintains the specified distance. ACC is often accompanied with a forward collision warning system that alerts the driver in case of an obstruction hazard ahead. It may even start to apply the brakes if the driver fails to do so.
Research is taking place that combines ACC with inter-communications between vehicles.. With communications added, ACC becomes Co-operative Adaptive Cruise Control (CACC). Communications allow the front vehicle’s rate of acceleration or deceleration to be communicated in real-time to the vehicle following (several times per second). The real advantage of CACC is to reduce delay in the response of the vehicle behind.
Some high-end new cars on the market now include lane departure warning systems and lane-keeping support systems. These keep track of the vehicle’s position relative to the running lane. They use a suite of sensors such as video sensors mounted behind the windshield, laser sensors on the front of the vehicle, and/or infrared sensors under the vehicle. Warning systems only sound if the vehicle starts to deviate from the lane, whereas lane-keeping support systems may take remedial action to return the vehicle to a safe position within the lane.
By combining technologies, the next evolution in vehicle control systems is autonomous or self-driving vehicles.
The US National Highway Traffic Safety Administration (NHTSA) has defined five levels of automation to describe systems with varying degrees of autonomyin the following way:
The Google car is an example of what is in development and on trial in California. youtube (See Video)
Digital mobile telecommunications are having a profound effect on the operating environment for ITS by enabling Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications. The combination of the two is sometimes referred to as V2X communications – meaning networked wireless communications between vehicles, the infrastructure (roadside units and traffic control centres) and passengers’ personal communications devices. A vehicle can broadcast data describing its position, movements and manoeuvres – and share this with other vehicles to prevent collisions, and with the infrastructure to optimise traffic control.
The ability to send and receive this data enables intelligent vehicle systems to integrate information from navigation systems with data from on-board sensors and information received from the infrastructure. This provides vehicle systems with an awareness of its immediate surroundings, including areas which may not be visible to the driver – which can be used to assist the driver to drive more safely. If the vehicle systems anticipate an accident they can, as a minimum, prepare safety systems and, perhaps, intervene to prevent an accident.
The technologies needed to implement a connected and Cooperative Vehicles (CV) environment fall into four separate components:
The OBE are:
Some of the vehicle-based information can be obtained from GPS or other similar sensors (for example location, speed, and direction), whereas other information (for example acceleration, instantaneous fuel consumption, anti-lock brakes activation, wiper status) may be obtained from vehicle engine scanning tools and other systems monitoring the vehicle’s different subsystems.
Connected vehicles are instrumented with a wide range of sensor technologies to enable applications aimed at improving safety and efficiency – including:
Roadside units and equipment are infrastructure systems that communicate with vehicles and collect data from the vehicle. Roadside equipment can support infrastructure-based applications – or applications involving co-operation between vehicles and the infrastructure (such as intersection collision avoidance systems, and eco-signals which inform approaching vehicles about the remaining green-light time to enable drivers to adjust their speed). Roadside equipment also supports remote applications by communicating information collected from the vehicles to a central location for processing. They also may help support the security and integrity of cooperative vehicle systems.
The communications network is the infrastructure needed to provide connectivity between vehicles (V2V), between vehicles and the infrastructure (V2I), and between roadside equipment and other parts of the system (V2X). Wireless communications are required for V2V and V2I communications, whereas roadside equipment may use wireless or wired networks.
The Connected Vehicles Initiative – USA
In the USA, the focus has been on using Dedicated Short-Range Communications (DSRC) for cooperative vehicle systems. Similar to Wi-Fi, DSRC is an open-source protocol for wireless communication. However, the big difference is that DSRC is intended for highly secure and high-speed communications – features that are critical for safety applications. DSRC has the following beneficial features:
low latency (as low as 0.02 seconds)
robustness in the face of interference
dedicated bandwidth protection (depending on bandwidth allocations in the country concerned)
In the USA, in 2004, the Federal Communications Commission, dedicated 75 MHz of bandwidth at 5.9 GHz, to be used for the Cooperative Vehicles initiative.
The rapid progress in mobile telecommunications means that the connected vehicle is no longer a research concept but a reality. Applications fall into four different, but not necessarily separate, categories:
connected vehicle safety applications – examples include driver advisories, driver warnings, and vehicle and/or infrastructure controls (See Driver Support);
connected vehicle mobility applications that use real-time data. The data are transmitted to vehicles wirelessly and are used by information service providers to broadcast current traffic conditions for satellite navigation systems. Data obtained from connected vehicles also has value for network management activities and for traffic engineers to optimise the performance of the transport system (See Probe Vehicle Measurements);
connected vehicle environmental applications that use real-time data from vehicles to support the development, operation, and use of "green" transport applications (See Smart Network Operations);
commercial applications that enhance the way business is conducted and open up new market areas – such as location-based added value services (See Location Based Services).