Intelligent speed assistance (ISA), or intelligent speed adaptation, also known as alerting, and intelligent authority, is any system that ensures that vehicle speed does not exceed a safe or legally enforced speed. In case of potential speeding, the driver can be alerted or the speed reduced automatically. Intelligent speed assistance uses information about the road to determine local speed limits. Information can be obtained from knowledge of the vehicle position, taking into account speed limits known for the position, and by interpreting road features such as signs. ISA systems are designed to detect and alert a driver when a vehicle has entered a new speed zone, or when different speed limits are in force according to time of day and conditions. Many ISA systems provide information about driving hazards, e.g. high pedestrian movement areas, railway crossings, schools, hospitals, etc., and limits enforced by speed and CCTV cameras at traffic lights. The purpose of ISA is to assist the driver to maintain a safe speed.
History ISA was born in France when Saad and Malaterre (1982) carried out their study of driver behaviour with an in-car speed limiter. Actually, they did not really test Intelligent Speed Adaptation, because the system did not automatically set the correct speed limit; instead drivers had to set the limiter themselves, and, rather like a cruise control, they could set it as they chose. After that there was roughly a ten-year gap until research on ISA was resumed in Sweden in the early 1990s. There followed a series of projects in Sweden, culminating in the large-scale trial of 1999 to 2001, when there were close to 5000 ISA-equipped vehicles on Swedish roads (Biding and Lind, 2002). Most of these vehicles were equipped with an informative or warning version of ISA, but a few hundred used an intervening system, being fitted with a haptic throttle, whereby the accelerator pedal became stiffer when the speed limit was exceeded. A kick-down function was provided to allow drivers to overcome this resistance. After ISA regulation entered into force in the EU on 8 July 2022, a speed limiter ISA law entered into force in the UK on 6 July. Regulation did not enter into force the same day, due to Brexit.
Terminology Intelligent speed adaptation is the terminology of the British Standards Institute, while the EU refers to intelligent speed assistance, in regulation (EU) 2019/2144 of the European Parliament.
Active and passive ISA Passive systems warn the driver when the vehicle is travelling in excess of the speed limit. Active systems slow the vehicle's speed to conform with the speed limit. Passive systems allow the driver to make a choice on what action should be taken. These systems usually display visual or auditory cues and warnings, which and may include tactile cues such as vibration in the accelerator pedal. Some passive ISA technology trials have made the accelerator pedal stiffer, to alert the driver. Most active ISA systems allow the driver to override the ISA when deemed necessary. This is thought to enhance public acceptance and safety, but leaves a significant amount of speeding unchecked. Both active and passive ISA systems can serve as on-board vehicle data recorders, retaining information about vehicle location and performance, for later checking and fleet management purposes.
Speed and location determination and verification There are four types of technology available for determining local speed limits on a road and the speed of the vehicle:
Position-based systems Radio beacons Optical recognition Dead reckoning
Position-based systems GPS like other satellite navigation systems is based on a network of satellites that constantly transmit radio signals. GPS receivers pick up these transmissions and compare the signals from several satellites in order to pinpoint the receiver's location to within a few meters. This is done by comparing the time at which the signal was sent from the satellite to when it was picked up by the receiver. Because the orbital paths of the satellites are known, the receiver can perform a calculation based on its distance to several of the orbiting satellites and therefore obtain its position. There are currently 31 satellites making up the GPS network, and their orbits are configured so that a minimum of five satellites are available at any one time for terrestrial users.
Radio beacons Roadside radio beacons, or bollards, work by transmitting data to a receiver in the car. The beacons constantly transmit data that the car-mounted receiver picks up as it passes each beacon. This data could include local speed limits, school zones, variable speed limits, or traffic warnings. If sufficient numbers of beacons were placed at regular intervals, they could calculate vehicle speed based on how many beacons the vehicle passed per second. Beacons could be placed in/on speed signs, utility poles, other roadside fixtures, or in the road itself. Mobile beacons could be deployed in order to override fixed beacons for use around accident scenes, during poor weather, or during special events. Beacons could be linked to a main computer so that quick changes could be made. The use of radio beacons is common when ISA systems are used, to control vehicle speeds in off-road situations, such as factory sites, logistics and storage centres, where occupational health and safety requirements mean that very low vehicle speeds are required in the vicinity of workers, and in situations of limited or obscured visibility.
Optical recognition systems Optical recognition technology has focused on recognizing speed signs, road markings and roadside objects such as "cat's eyes". This system requires the vehicle to pass a speed sign or similar indicator and for data about the sign or indicator to be registered by a scanner or a camera system. As the system recognizes a sign, the speed limit data is obtained and compared to the vehicle's speed. The system uses that speed limit until it detects a speed sign with a different limit. It is also possible to use computer vision to determine the assured clear distance ahead.
… excerpt ends here. Continue reading the full article.
