Vehicle Safety Systems

Transcription

1 Vehicle Safety Systems September 2009 SECC and Glasgow Science Centre The UKRO authorises the use of the educational information contained within this document, however reference must be given to UKRO with the use of the UKRO logo

2 1. Introduction The aim of this document is to provide current (2009) information in relation to modern day car safety systems, and the difficulties such systems pose for the UK s Professional Rescuers. We will consider the influences of: Primary Safety Systems - systems that are being included to avoid the vehicle being in a crash. Secondary Safety Systems - systems that aim to reduce the impact of a crash upon its occupants. The information contained within this handout is being made available through the UKRO and its partnership organisations. Should you wish to receive further information please contact Dick Dawson who is part of the UKRO Education Committee (ddawson@ukro.org) 2. Why Do Safety Systems Exist? In the UK there are 2,700 deaths, and 30,000 serious injuries associated with car collisions, reported each year. Although these figures are a stark reminder of the dangers which face the average car user, there are number of more powerful influences which dictate what systems are manufactured into the modern vehicles. Consumers demand safer vehicles for themselves and their families, and it is their sales pattern that dictates the success of manufacturers Manufacturers gain additional marketing value, by introducing systems to beat competitors and win additional consumers. Governments legislate not only for responsible driving e.g. penalties for drink driving and drug abuse, speeding etc, but stipulate a requirement for basic safety systems e.g. seat belts, in an effort to reduce the burden of cost on society associated with casualties involved with car collisions. Premium loadings on vehicle insurance by large insurance bodies in relation to cost of damage/injuries by vehicle type e.g. 85% claims relating to personal injury are for Whiplash injuries. Page 2

3 3. Primary Safety Systems Technology that helps to avoid/prevent a crash from occurring New technologies now coming forward will have a significant effect on the way the public view crash safety with cars being able to avoid or mitigate (reduce) the likelihood of a crash occurring in the first place. Primary systems focus purely on the need to prevent the vehicle when mobile from being involved in a collision: a. Electronic Stability Control (ESC) b. Adaptive Cruise Control c. Lane Departure Warnings d. Driver Alert Systems e. Night Vision with Pedestrian Detection f. Low Speed Avoidance Systems Electronic Stability Control Over 3,000 young drivers aged under 25 are killed or seriously injured on UK roads annually. One of the biggest accident types for young drivers is single vehicle accidents involving loss of control. ESC a system designed to apply braking to individual wheels aims to help prevent a skid or spin. New and young drivers most commonly drive small cars that are cheaper to buy and to insure. Small cars are less safe because of their size. Small cars are also less likely to have ESC fitted as standard, which is a vital safety feature. A first car is often second hand, which makes it even more difficult for young drivers to choose a car fitted with ESC. Yet these young drivers are most likely to be involved in the type of loss of control crashes where ESC could help to prevent the crash. Young people drive poorly equipped cars. Research centre, Thatcham have undertaken on behalf of the UK insurance companies an assessment of vehicles being produced for the UK s roads. These fitment ratings show there are only 5 supermini models with ESC fitted as standard. These are the Mini Hatch, Mini Clubman, Peugeot 1007, Smart For Two, and the Suzuki Splash. From the 47 supermini models rated, these represent only 11% and only a very small choice for the buyer. Department for Transport research data has shown that vehicles equipped with ESC are 25% less likely to be involved in a serious or fatal crash. Currently, ESC is fitted as standard on only 53% of new cars on sale in the UK today. The system costs on average 425 to fit as an option, but the cost of the components is well under 100, so why don't all vehicle manufacturers fit it as standard? New Page 3

4 regulations will see that all vehicles manufactured from 2010 onwards will have to be equipped with a system for ESC. It is estimated that such systems will reduce the number of serious crashes and contributes to improved road safety by: 380 fewer fatalities in the UK annually 1,100 fewer serious injuries 7,800 fewer crashes overall. Adaptive Cruise Control Adaptive Cruise Control is a system that links the common cruise control system with a 77 GHz radar fitted at the front of the vehicle. Essentially a comfort feature, ACC allows the driver to pre-set a speed in changing traffic conditions, with the vehicle autonomously. This system maintains a safe distance between itself and the vehicle it is following, whatever the speed of the prevailing traffic. The latest generation of these systems have full stop/go functionality, your car coming to a complete stop when its path is blocked. The car will then start moving again once traffic conditions allow, thus always maintain a safe distance. This system can also incorporate the Collision Mitigation Braking System which will warn the driver visually and audibly that a potential collision is imminent. in some cases, the system will apply up to 70% of available braking power in an attempt to avoid or mitigate the crash. Many systems will pre-charge seat belts, airbags and brake systems to obtain optimum performance in the event of a collision. The ACC systems are not a set and forget system, in so far as they do rely on the driver to pre-set the controls for speed preferred and to monitor the vehicle at all times. Page 4

5 Lane Departure Warnings This safety system aims to keep a moving vehicle within lane marking on the road and help protect the occupants if the driver is distracted or tired. The system operates between mph and provides a continuous warning beep when the car is about to cross the road markings. If there is no response from the driver the system takes control of the electric power steering and calculates the optimum steering torque to keep the car in the centre of the lane. It should be noted that such lane keep assist systems are not there to drive the vehicle, and to prevent abuse of the system it will switch itself off if the driver takes their hands off the wheel for longer than a few seconds. It is not there to replace the driver completely. Additionally, the system does not intervene if the indicators are used or if positive steering movements are made. Driver Alert Systems With the increasing use of vehicles on britains roads, and longer journeys being made, accidents due to driver drowsiness are a common occurance. A number of vehicles now incorporate a Driver Alert system which monitors the actions of the driver and gives warnings that their physical condition may have an adverse effect on their ability to react to road situations. Volvo Driver Alert System Page 5

6 Some systems use a camera located near to the rear view mirror to monitor the driver, other systems monitor the driving behaviour for patterns during the first few minutes of every journey and then compares ongoing driving against this pattern. Warnings are active on systems from 40mph upwards to 113mph. Mercedes Attention Assist System Night Vision with Pedestrian Detection BMW have recently introduced to a number of their vehicles a safety system to prevent vehicles impacting on pedestrians in the dark. The systems have been tested with other heat signatures such as those from animals in roadside fields etc and has proved very accurate. It should be noted that such system need not be used in isolation and manufacturers will be looking to package all safety systems to ensure that the vehicle has the greatest opportunities available for crash avoidance. Low Speed Avoidance System In an effort to prefent low speed collisions and impacts with pedestrians, a number of vehicle manufacturers have designed and integrated the autonomous emergency braking system. This system prevents the car from coming into contact with other objects during low speed travel. This is a represents a major step in the future of accident and casualty reduction on UK s roads. One system currently on the market is Volvo s City Safety system. This unique system is designed to chiefly address the most common crash type, the low speed fender bender. Typically occurring at speeds below 20mph these accidents represent 75% of all crashes and such a system fitted to all cars could significantly reduce whiplash injuries and repair costs. This system uses low cost laser radar Page 6

7 (LIDAR) mounted behind the windscreen (and so out of harm s way). It constantly monitors the road ahead. once an object is within 6 metres, the system calculates whether the driver is reacting to avoid it. if not, the system will autonomously apply up to 50% of the braking power, enough to completely avoid contact at 10mph and mitigate the effects of a 20mph crash by 50%. The potential for the reduction of whiplash injuries and damage repair costs is considerable. 4. Secondary Safety Systems Technology that helps the human occupant survive the forces of an inevitable crash These system focus purely on the need to protect the occupant in a crash: a. Airbags b. Seatbelt pre-tensioners c. Anti Whiplash Seats d. Stronger Occupant Compartments e. Automatic Collision Notification Systems Page 7

8 Airbags Driver's airbag The driver's airbag is integrated in the impact absorber on the steering wheel. An acceleration detected in the sensor is integrated and evaluated. The driver's airbag is fired once the appropriate triggering thresholds have been exceeded. The actuator receives a firing voltage from the airbag control unit or from the relevant satellite. This releases stored pressure of the inert gas from the cartridge which escapes through the airbag, inflating it. When the airbag inflates, the cover (impact absorber of driver's airbag, cover of passenger airbag, trim of side/head airbags) splits open at the programmed rupture point. The talc from the airbag that is deposited in the passenger compartment is non hazardous. Professional rescuers should always consider the use of airbag restaint systems and ensure that crews working in the vacinity of airbags adhere to the national guidance of rule. This is 5 inches from the side airbag, 10 inches from the drivers airbag, 15 inches from the curtain airbag and 20 inches from the passenger airbag. Passenger airbag The passenger airbag is located in the instrument panel above the glove compartment on the passenger side. A seat-occupancy detector has been integrated for years in order to prevent unnecessary triggering of the passenger airbag in the event of a crash (passenger seat is not occupied). The front passenger seat is identified as being occupied from a weight of 12 kg by the sensors in the front passenger seat and through evaluation of the data in the airbag control unit or in the satellite and the system is thereby activated. Page 8

9 Side airbag The side airbags are located behind the side trims in the doors and in the backrests of the driver's and front passenger seats. In the event of a side impact, the transversal acceleration that occurs is measured by appropriate sensors. If the triggering threshold is exceeded, the airbag control unit or the relevant satellites fire the side airbags and, if fitted, also the head airbag. Head Airbag The ITS (Inflatable Tubular Structure) and AITS (Advanced Inflatable Tubular Structure) head airbags are installed along the A-pillar and the roof frame on the driver's and passenger sides and are fired with the corresponding side airbags. With an additional head airbag at the rear, the airbag is installed along the A-pillar, the roof frame and the C-pillar. Unlike the other airbags, the ITS head airbag is a tubular system which is secured to the body with belt straps. The AITS head airbag is a head protection system like the ITS with the advantage of the area protection afforded by a curtain. When the generator is fired, this increases the diameter of the head airbag, thereby reducing its overall length. With this procedure, the head airbag stretches between the lower end of the A-pillar and the rear attachment to the roof frame. Unlike front and side airbags, which collapse relatively quickly after inflating, the head airbag retains the gas volume and thus also offers protection in the event of the car rolling over or secondary accidents. The head airbag can be cut off at the belt straps or cut through safely. Rear Curtain Airbag in 2008 the Toyota IQ launched featuring the first ever rear curtain airbag to protect the rear occupants heads in the event of a rear impact. Page 9

10 Airbag Disconnection Times - a general guide Page 10

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14 Seatbelt Pre-tensioners The purpose of seatbelt is to ensure that the occupant of a seat is held in the correct position so that in the event of a collision, the risk of persons submarining is minimised and inertial energies are spread throughout the whole SRS system in a controlled manner i.e. seatbelt restraints, airbag deployments etc. In order to maintain the seat occupant in the safest position on the seat, seatbelts make use of pre-tensioners, and in recent vehicles employ electronic sensors to measure the speed and pressures applied upon the seatbelt in the event of an impact. This allows a control module on the vehicle to deploy the other safety systems at the appropriate time for the position of the seat occupant, and for the occupant s body to be restrained with a measured force across the seat belt. If the body is restrained by the belt with excessive force, then the body and its internal organs could suffer an injury. Likewise if the belt force limiter is set too low, the body could be thrown forward too quickly against the airbag or surrounding vehicle structures. Three types of system are used in the vehicles to reduce belt slack: Mechanical seatbelt tensioners The seatbelt tensioners are unlocked mechanically and tighten the seat belts. Pyrotechnical seatbelt tensioners The seatbelt tensioners are fired by the airbag control unit or the seat satellites, a pyrotechnical unit tightens the seat belt. Page 14

15 Pyrotechnical anchor-fitting tensioners 1 Seatbelt tensioner not triggered 2 Seatbelt tensioner triggered The anchor-fitting tensioners are fired by the seat satellites, a pyrotechnical unit tightens the seat belt. Pyrotechnical seatbelt tensioner Pyrotechnical anchor-fitting tensioner Anti Whiplash Seats There is currently considerable research being undertaken by Thatcham Research Centre into the effects of seat design and their influences on whiplash injuries. In an effort to reduce the likelihood of C Spine injuries occuring there are a number of clever head restraint designs that become active if a rear-end collision is anticipated. Such restraints are now standard in many Mercedes models e.g. C- Class, CLK E-Class, CLS and S-Class. Page 15

16 Unlike existing active restraints that move forward in reaction to a collision, the systems such as the Neck Pro system, monitors the vehicle sensors and predicts when a crash is about to happen. It then releases pre-tensioned springs inside the headrest, causing the headrest to move forward by 40mm and upwards by 30mm providing better support for front seated occupants. Rescuers are likely in the future to come across vehicles with such active headrest arrangements and should consider the risks involved from headrests which have not yet actuated. Historically where the headrest is used as part of a point of stability whilst immobilising the C spine with the rescuers hands, such headrests may prove an obstacle to utilising existing techniques. Stronger Occupant Compartments There are a number of factors that contribute to the continuing development of vehicle body designs, as are shown in the body development picture above. Such demands on vehicle manufacturers dictate the materials that need to be considered when building a vehicle which has led to a growth in the use of aluminium and boronated steel materials. Such material usage has greatly enhanced the strength of occupant compartments but with it come complications for the professional rescuer. Page 16

17 For further information on the complexities of boronated vehicle construction, reference should be made to the UKRO New Vehicle Technologies Package which can be located within the Education section of the UKRO website Advanced Automatic Collision Notification Systems The advanced automatic collision notification system monitors a vehicles sensors for information which may prove useful in the event of a crash. Information from seat sensors for the number of passengers, airbag deployments, seat belt pretensioner deployments, vehicle orientation, number of rolls, speed of impact, delta velocity, GPS etc are collated and then sent to a communications centre to alert them that the vehicle has been involved in a crash. One of the first manufacturers to introduce the automatic collision notification system to their vehicles is BMW. Their enhanced ACN sends additional information from the vehicles control units automatically to the BMW assist response centre operated by ATX Communications. There the data is evaluated and can be passed onto emergency services who would be on route. As such systems become more commonplace, this will provide the responding Incident Commander greater time for consideration of the priorities they will be faced with when they arrive on scene. This system will be featured on most 2009 and later BMW models, and is featured on models from manufacturers such as Ford and Lexus. This represents the next step forward in the rapid and appropriate deployment of emergency response following a vehicle accident. Page 17