La vulnérabilité et la protection du rachis cervical chez les motocyclistes

Abstract

For a number of years motorcyclists have been vulnerable and over-exposed on the open road. Powered Two-Wheelers accidents can inflict serious injury, in particular, to the cervical spine, with possible damage to the neurological system. In addition, cervical trauma has been linked to the highest mortality rates for motorcyclists, in comparison with other injuries (accidentrelated issues/effects). Even non-fatal accidents can leave the victim tetraplegic, irreversibly affecting their physical well-being, culminating in long term disability which can easily become a heavy financial burden. Even today, the cause and effects of cervical injuries to motorcyclists remain somewhat unknown. We do know that the majority of these types of injuries are caused by a direct impact to the rider’s helmet. Different protection devices are currently available on the market to reduce the risk of serious cervical injury. However, the lack of governing bodies and standardization in safety regulations largely discredits the protection value publicized by retailers. On top of this, it would appear that the protection devices cannot be adapted to all types of Powered Two-Wheelers. In light of these observations, this thesis proposes to answer the following question: How does one improve cervical spine protection for motorcyclists without causing detriment to vehicle and rider safety or the riding experience? In order to answer this question, a method of evaluation for testing neck braces was elaborated. Numerical and experimental evaluation was performed, touching on two fundamental aspects: the devices capacity to protect the motorcyclist against cervical trauma and its impact on rider safety and riding experience. Four main phases were outlined to achieve the objective announced previously. The first phase consisted in establishing a functional design requirements specification to formalize the need for reinforcing cervical spine protection without impacting on safety or the riding experience (O1). The formulation of this document lead to seven criteria for evaluation: qualitative protection, quantitative protection, riding visual safety, device bulkiness, device weight, device range of adjustment and size. Scores (from 0 to 5) were determined for each of these criteria using a grading system to evaluate each of their performances. The second phase aimed at establishing a method to evaluate the different protection criteria and the level of safety/riding satisfaction experienced by the motorcyclists (O2) both numerically and experimentally. The qualitative and quantitative criteria were evaluated numerically through simulation using a finite element human body with real-case loading, representative of trauma cases suffered by victims of motorcyclist accidents. Simulations were computed both with and without protection devices. This study focused on comparing the type of lesion/laceration on the cervical spine and also the stress – strain factor in different anatomical regions of the neck. The five other protection criteria were evaluated experimentally. Riding visual safety was assessed by observing the articular mobility in the neck region both with and without protection devices in two different riding positions (one on a scooter and one on a racing motorbike). Device bulkiness, weight, range of adjustment and size were simply measured on the devices themselves. Weighting coefficients, from the requirements specifications document were then applied to the scores obtained for all criteria before a final performance grade was determined. The third phase included a full evaluation of 2 different protection devices using the method elaborated previously (O3). This led to a complete analysis of protection devices from both reputable leaders EVS and Leatt Brace, still available on the market today. Even though these devices display a satisfactory level of safety and riding experience, the results concerning the original design criteria of cervical protection, were revealed to be less than adequate. Worse still, they proved to increase cervical vulnerability to injury in specific loading scenarios, making their sale and use as a motorcycle cervical protection device contestable. The third phase gave feedback on both the pros and cons of the method established previously, promoting further improvements. The fourth and final phase of the current work focused on the development and design of a new cervical protection device for motorcyclists (O4). Preliminary work was conducted in three steps; research into protection solutions, preselection of promising concepts and the ground work for an actual design. This phase triggered the creation of two prototypes which where both partially evaluated using the method described previously. The prototyping stage should be continued and the design refined until a complete evaluation is possible, only then, can a final decision be reached regarding the recent innovative process. The results generated within the parameters of the current thesis have succeeded in establishing a precise identification of the expectations surrounding a cervical protection device for motorcyclists. These expectations, were translated into criteria, and played a key role in the development of a novel method of evaluation for current protection devices. The seven unique criteria, characterizing the ability to protect the spine, vehicle safety and riding experience were evaluated thanks to the newly developed method using both numerical and experimental testing. The method was applied to two existing, readily-available protection devices. Results showed design deficiencies and shortcomings in their ability to protect the motorcyclist cervical spine, making the products potentially non-viable for commercial use. In light of the results, prototypes and concept builds for a new protection device were partially tested. Their design must be refined before a complete evaluation can take place and a final decision reached on the future protection device to be developed.

Date	22 Jul 2021
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Yvan Petit (Supervisor), Pierre Jean Arnoux (Supervisor) & Éric Wagnac (Co-supervisor)