Intelligent speed adaptation
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Intelligent speed adaptation (ISA), 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, a human driver can be alerted, or the speed reduced automatically.
Intelligent speed adaptation uses information about the road to determine the required speed. 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 also 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.
Enforcing speed limits strictly enough to eliminate slight overspeed is difficult; it is proposed that ISA will assist with this. It is also argued that speed limits need to be properly set as those too low will equally cause issues. Drivers maintaining speeds significantly below a posted limit have been shown to have an increased accident risk compared to those nearer the limit (including those slightly over the limit).
- 1 Active and passive ISA
- 2 Speed and location determination and verification
- 3 Limitations
- 4 Benefits
- 5 Commercial use
- 6 Government implementation
- 7 See also
- 8 External links
- 9 References
Active and passive ISA
The two types of ISA systems differ in that passive systems simply warn the driver of the vehicle travelling in excess of the speed limit, while active systems intervene and correct the vehicle's speed to conform with the speed limit. Passive systems are generally driver advisory systems: They alert the driver to the fact that they are speeding, provide information as to the speed limit, and allow the driver to make a choice on what action should be taken. These systems usually display visual or auditory cues, such as auditory and visual warnings and may include tactile cues such as a vibration of the accelerator pedal. Some passive ISA technology trials have used vehicles modified to provide haptic feedback by making the accelerator pedal stiffer when appropriate to alert the driver. Most active ISA systems allow the driver to override the ISA when deemed necessary; this is thought to enhance acceptance and safety, but leaves a significant amount of speeding unchecked.
An often unrecognised feature of both active and passive ISA systems is that they 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:
GPS 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 very accurately, 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. Four satellites are the minimum required to determine a precise three-dimensional position.
The popularity of in-car navigation systems may give the impression that GPS is flawless, but it is subject to a number of fundamental problems.
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 and road markings; other roadside objects, such as the reflective "cats' eyes" that divide lanes could possibly be used. 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 would use the speed limit from the last sign passed until it detects and recognizes a speed sign with a different limit.
If speed signs are not present, the system does not function. This is a particular problem when exiting a side road onto a main road, as the vehicle may not pass a speed sign for some distance. There can also be a problem taking a vehicle from a Miles Per Hour (MPH) country to a KiloMetres per Hour (KMH) one and vice versa, particularly if it is difficult or impossible to adjust the system to use the correct measurement.
Dead reckoning (DR) uses a mechanical system linked to the vehicle's driving assembly in order to predict the path taken by the vehicle. By measuring the rotation of the road wheels over time, a fairly precise estimation of the vehicle's speed and distance traveled can be made. Dead reckoning requires the vehicle to begin at a known, fixed point. Then, by combining speed and distance data with factors such as the angle of the steering wheel and feedback from specialized sensors (e.g., accelerometers, flux gate compass, gyroscope) it can plot the path taken by the vehicle. By overlaying this path onto a digital map, the DR system knows approximately where the vehicle is, what the local speed limit is, and the speed at which the vehicle is traveling. The system can then use information provided by the digital map to warn of upcoming hazards or points of interest and to provide warnings if the speed limit is exceeded.
Dead reckoning is prone to cumulative measurement errors such as variations between the assumed circumference of the tyres compared to the actual dimension (which is used to calculate vehicle speed and distance traveled). These variations in the tyre circumference can be due to wear or variations in tyre pressure due to variations in speed, payload, or ambient temperature. Other measurement errors are accumulated when the vehicle navigates gradual curves that inertial sensors (e.g. gyroscopes and/or accelerometers) are not sensitive enough to detect or due to electromagnetic influences on magnetic flux compasses (e.g., from passing under power lines or when travelling across a steel bridge) and through underpasses and road tunnels.
Some top-end GPS-based navigation systems currently on the market use dead reckoning as a backup system in case the GPS signal is lost.
An initial reaction to the concept of ISA is that there could be negative outcomes, such as driving at the speed limit rather than to the conditions, but numerous ISA trials around the World have shown these concerns are unsubstantiated.
A particular issue is that most ISA systems use a speed database based purely on information regarding the posted maximum speed limit for a roadway or roadway segment. Many roads have features such as curves and gradients where the appropriate speed for a road segment with these features is less than the posted maximum speed limit. Increasingly, road authorities indicate the appropriate speed for such segments through the use of advisory speed signage to alert drivers on approach that there are features which require a reduction in travelling speed. It is recognised that the speed limit databases used in ISA systems should ideally take account of posted advisory speeds as well as posted maximum speed limits. The New South Wales ISA trial, underway in the Illwarra region south of Sydney currently, is the only trial that is using posted advisory speeds as well as posted maximum speed limits.
Some car manufacturers have expressed concern that some types of speed limiters take control away from the driver. Some ISA systems do have provision for over-ride by the driver in the event that the set speed is inappropriate.
For some traffic safety practitioners, active intelligent speed adaptation is thought to be an example of 'hard automation', an approach to automation that has been largely discredited by the Human Factors community. An inviolable characteristic of human users is that they will adapt to these systems, often in unpredictable ways. Some studies have shown that drivers 'drive up to the limits' of the system and drive at the set speed, compared to when they are in manual control, where they have been shown to slow down. Conversely, the experience of some drivers with driving under an active ISA system has been that they find they can pay more attention to the roadway and road environment as they no longer need to monitor the speedometer and adjust their speeds on a continuing basis.
There is also concern that drivers driving under speed control might accept more risky headways between themselves and vehicles in front and accept much narrower gaps to join traffic (this fact drawing particular criticism from motorcycling groups).
Wider criticism also comes from the insistent focus on speed and that road safety outcomes could be better achieved by focusing on driving technique, situational awareness, and automation that 'assists' drivers rather than 'forces' them to behave in particular ways. Intelligent speed adaptation has also been held as an example of a technology which, like speed cameras, can often alienate the driving public and represents a significant barrier to its widespread adoption.
Some studies which pre-date the development of ISA systems indicated that drivers make relatively little use of the speedometer and instead use auditory cues (such as engine and road noise) to successfully regulate their speed. There is an argument in the literature that suggests that as cars have become quieter and more refined speed control has become more difficult for drivers to perform. Thus an alternative 'soft-automation' approach is simply to re-introduce some of those cues that drivers naturally use to regulate speed (rather than incur the expense and unexpected behavioral adaptations of ISA).
A British study estimates that ISA could reduce fatalities by half.
RTA (NSW Australia) ISA trial results showed the benefits of ISA are improved speed zone compliance with reduction in the level and duration of speeding.
A cost-benefit analysis of ISA (in Australia) published in April 2010 by the Centre for Automotive Safety Research suggested advisory ISA would reduce injury crashes by 7.7% and save $1,226 million per year. These figures were 15.1% and $2,240 million for supportive ISA and 26.4% and $3,725 million for limiting ISA.
The confirmation by the Australian research of the benefits of ISA have resulted in the recommendation for wider adoption and promotion of ISA in the Australian National Road Safety Strategy 2011-2020.
ISA sees widespread commercial use in Australia. This advanced commercialisation of ISA has in part been underpinned by initiatives from the various state roads authorities, and the inclusion of ISA in the National and State Road Safety Strategies.
SpeedAlert is a passive ISA product marketed by Smart Car Technologies, based in Sydney NSW. It offers full national speed zoning information embedded within a GPS-based navigation system, providing drivers with information on speed limits and vehicle speed, as well as related information on locations such as schools, railway level crossings, and speed camera sites.
SpeedShield is an active ISA product marketed by Automotion Control Systems, based in Melbourne, Vic. It offers speed zoning information embedded within a GPS-based navigation system, providing drivers with information on speed limits and vehicle speed and is combined with technology that intervenes and controls the vehicle speed to no faster than the posted speed limit for that section of roadway. The technology is generally transferable across vehicle manufacturers and models, but must be configured for an individual make and model.
Coredination ISA is a passive ISA product marketed by Coredination, based in Stockholm, Sweden. This product is built as a smartphone-application for Android and iPhone. It offers full national speed zoning information, providing drivers with information on speed limits and vehicle speed. The product is very lightweight and no separate hardware or fixed installations are necessary.
As of 2012, five out of the 35 governments associated with the ETSC agreed to introduce ISA in all vehicles.
As of 2013 adoption of the technology was being considered by the European Commission but was being strongly opposed by UK transport secretary, Patrick McLoughlin. A government spokesman described the proposal as "Big Brother nannying by EU bureaucrats." In 2019 however, it was finally agreed to adopt the new technology in all new cars by 2022
- Advanced driver-assistance systems
- Intelligent transportation system
- Intelligent vehicle technologies
- Map database management
- Speed limiter
- Traffic sign recognition
- Usage-based insurance
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