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Child restraint -systems: a matter of priority

   
 
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Increasingly "true-to-life" dummies which provide the manufacturers of restraint systems and airbags with much more accurate information.
Why is it that restraint systems designed for young passengers which, on the basis of tests, should provide effective protection in 70% to 80% of accidents only offer real protection in 30% to 50% of cases? How can we improve the various safety devices installed in vehicles and intended for passengers under the age of ten? How can we make the tests more reliable - in particular, by improving the reliability of the dummies used in the tests? These questions are being analysed by a group of manufacturers, university laboratories and European research centres working together under the CREST project. The aim: to place on the market, as swiftly as possible, restraint systems that are reliable, comfortable and easy to use.

 

Head-on collision on a country road between two vehicles travelling at speeds of 60 km/h and 75 km/h. In the first vehicle, a seven-year-old child travelling on the rear bench seat without any restraining system escapes unscathed. In the second, a little girl of five and a baby of eight months are both strapped in child seats -and are both injured. This accident is one of the hundreds of accidents on which data have been collected by the European CREST project. Launched in 1996 with the support of the Standards, Measurements and Testing Programme, and scheduled to last for four years, this huge partnership brings car manufacturers, university laboratories and public research centres together. Their aim: to improve the safety of children in vehicles. "In order to understand, we first had to analyse. To this end, the researchers had to design their own tools. The first obstacle we encountered was the general lack of statistical information on road traffic accidents specifically involving children," explains Xavier Trosseille, an engineer at the Biomechanics Laboratory of the French motor manufacturers PSA Peugeot-CitroŽn/Renault, and the coordinator of the project.

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Reconstructing an accident in which the injuries suffered by children are known and documented and comparing the behaviour of the dummies used in these tests, helps to improve their reliability.

Analysis and reconstruction
CREST is involved in the activities following on from the work of the International Task Force on Child Restraining Systems which, back in 1990, had brought together top international experts working in the field of accident research (from Germany, Canada, the United States, France, the United Kingdom, the Netherlands and Sweden), a number of whom are also currently involved in the European project. The method has proved its worth by adopting the following strategy: case-by-case studies, based on as much available detail as possible, of accidents involving children restrained by specific devices, followed up by reconstructions in the laboratory with a view to understanding the causes of the traumas which these systems were unable to prevent. One result of the analysis, for instance, was that it highlighted the benefits of transporting very small children in a rear-facing position until they are two years old.

The urgency of the situation facing Europe

"The problem with this Task Force was that its work was proceeding so slowly in an area where rapid progress was vitally needed," Xavier Trosseille goes on. "This is why we proposed the launching of a specifically European project which, thanks to the support of the Commission, could benefit from close cooperation between manufacturers, universities and research centres."

The task is enormous, involving as it does the analysis of numerous types of injuries sustained in very different kinds of accidents and involving children varying in age - from 0 to 12 years. By the end of 1997, data on 188 cases had been gathered by six European teams based in four countries (France, Italy, Germany, United Kingdom) - the ultimate aim being to record data on nearly 400 cases. For laboratory reconstruction purposes, the accidents selected must include a sufficient number of precise elements (speed, type of impact, state of the vehicles after the accident, nature of the injuries, exact position of the children, etc.) The data are collected using a precise methodology designed to determine how injuries are related to the devices employed. Some twenty cases have already been reconstructed. The impact is reproduced, using identical vehicles and dummies. Additional tests with a catapult (a coach body mounted on a carriage to study the effects of deceleration) also make it possible to analyse in greater detail certain parameters such as the effects of the exact position of the seat or the way in which it was fixed in the vehicle. "This led, for example, to the discovery of the so-called submarining phenomenon," explains the project coordinator. "Young children placed on raised seats and restrained by factory-installed safety belts may, in the event of a violent impact, slide under these belts and suffer abdominal injuries. Conventional tests with dummies fail to reproduce this phenomenon."

"True-to-life" dummies
These painstakingly precise reconstructions enable us to study not only the performance of the safety systems but also the performance of the dummies designed for the past thirty years for evaluating restraint systems in accordance with the European regulations by TNO Automotive's Crash Safety Centre, one of the CREST partners.

"It was specifically with a view to reproducing this submarining phenomenon that modifications were made to the series P (P for Pinocchio) dummies corresponding to ages 3, 6 and 10," explains Michiel van Ratingen, Director of Research at the CSC. Improvements in the structures of the thorax and the pelvis were achieved thanks to biometric comparisons based on X-rays. Other types of measurements taken on children placed in restraint systems have prompted the researchers to reduce the rigidity of the thorax so as to make the dummies more impact-sensitive and to use others types of material - padding foam - to create a "true-to-life" consistency of the thighs and abdomen. Lastly, with the help of new instrumentation, it is possible to concentrate on acceleration phenomena (at chest level) and pressure phenomena (neck and abdomen).

"These modifications enabled us to design a prototype, on the basis of which we are beginning to produce a new series of dummies (type Q). Their reactions to impacts approximate much more closely to the reactions of children. Thanks to the instrumentation, it is possible to determine potential injuries with much greater precision, and behaviour studies are no longer restricted to frontal and rear impact but now include lateral impact. In fact, existing restraint systems are type-approved in accordance with a frontal impact procedure. Nothing has been designed to protect against lateral impacts which, while less frequent, are often more serious," adds Michiel van Ratingen.

These new dummies, which are more realistic and of better quality, will provide the manufacturers of restraint systems and airbags with much more accurate information, which in turn should lead to rapid improvements in the safety of young passengers.

 

 

Project Title:  
Child Restraint System for Cars

Programmes:
Standards, measurements and tests

Contract Reference: SMT4-CT95-2019

CORDIS databaseFor more information on this project,
go to the Cordis database Record

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