Crashworthiness Analysis of Three Prototype Ambulance Vehicles
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CRASHWORTHINESS ANALYSIS OF THREE PROTOTYPE AMBULANCE VEHICLES Nadine Levick Objective Safety LLC USA Raphael Grzebieta Monash University Australia Paper Number 07-0249 ABSTRACT could provide for major safety enhancements for ambulance vehicles. There is need for vehicle safety This paper is an evaluation of the predicted safety researchers, ambulance industry and vehicle performance of three USA prototype ambulance designers to recognize and apply these existing vehicles with aftermarket structural modifications. principles to reduce current failures in an important Expected safety performance was analyzed using and essential service that appears to have a poor existing and established automotive safety principles. safety record, considerably below that of other Information on design and construction of the passenger (Maguire 2003, Ray 2005, Levick 2006) vehicles was identified, and evaluated via application and also other commercial vehicles (FMCSA). of basic engineering crashworthiness principles and laws of physics, with a specific focus on INTRODUCTION countermeasure design for reducing harmful loading and injury causation potential in crashes or sudden Emergency Medical Service (EMS) vehicles, decelerations. Data sources used for the analysis ambulances, are an unusual vehicle in the included: vehicle specifications, inspections, transportation system for a number of reasons – they photographs, crash tests and published carry passengers in a number of orientations, are part crashworthiness and injury mitigation literature. of an emergency response system, are built primarily as aftermarket modifications to existing vehicles or Results demonstrated poor vehicle structural integrity have a ‘box’ secured to a light or heavy truck chassis and crashworthiness for these aftermarket modified (all conducted outside of the existing automotive ambulance vehicles. Assessed crashworthiness safety infrastructure), and are also occupational performance and occupant protection do not appear environments for the EMS providers. However, in the optimized even for the minimally structurally USA ambulance vehicle safety is addressed outside modified van. Current interior design features (seat of the Federal Motor Vehicle Carrier Safety design, patient transport device design, head strike Administration system – in regards to crash events zones and restraint systems) and layout, demonstrated and outcome data collection and hence do not share predictable serious crashworthiness and occupant the same comprehensive safety oversight of other protection hazards. commercial vehicles. These are projected findings, rather than actual Capture of safety performance of these vehicles is at crashworthiness tests – however this is the first best scant – and rudimentary at a national level and comparative automotive safety evaluation of has been demonstrated to be incomplete (McGuire prototype ambulance vehicles. This is key 2003). The data that has been published highlights information for a major fleet of vehicles globally that ambulances are associated with high crash which has had minimal automotive safety attention or fatality and injury rates per mile traveled and that input to date. compared to other emergency vehicles (Becker 2003) have high occupant fatality rates and that also From this study it appears there are major compared to trucks have almost double the deficiencies in safety design of these prototypes. percentage of occupant fatalities. It is recognized that Emphasis on a passenger compartment that has the hazards are greatest for occupants of the rear crashworthy features, effective seat design, based on compartment (Becker 2003). existing literature and a clear focus on occupant human factors and equipment location and anchors, Given this background and the existing, albeit scant, Levick 1 biomechanical and crashworthiness data that have a dangerous profession, and vehicles crashes have been published – the issue of identifying been shown to be the most likely cause of a work crashworthiness and occupant hazards has been related fatality in EMS (Maguire 2003). The most raised in a number of sectors. dangerous part of the ambulance vehicle has been demonstrated in both biomechanical and One response to this safety performance challenge epidemiological studies to be the rear patient has been for a spectrum of people to attempt to compartment (Becker 2003, Levick 2000-2006), address the occupant safety and crashworthiness of which currently is a part of the ambulance vehicle these vehicles and largely on an individual level . that is also largely exempt from the USA Federal However, as well intentioned as these initiatives have Motor Vehicle Safety Standards (FMVSS). Also, been , they have primarily involved small teams of unfortunately, no reporting system or database exists Emergency Medical Service end users and after specifically for identifying ambulance crash related market manufacturers and had very minimal, if any, injuries and their nature, so specific details as to input from key and recognized automotive safety which injuries occurred and what specifically were expertise, and very minimal application of in depth the mechanisms which caused them are scarce, and understanding of automotive safety and there is not yet a national system for this data capture crashworthiness principles. in the USA. EMS is a relatively new industry, an industry that has What we do know is that ambulances have high crash an unusual history of beginnings within the mortician fatality rates per mile, well above those of passenger industry. The first modern ambulances were hearses, vehicles, or even when compared to similar sized usually a Cadillac station wagon, a vehicle in which vehicles (Ray 412).- and there is approximately one an occupant could be transported in the recumbent ambulance crash fatality per week in the USA, and a position. Proximity and access to the patient was not number of serious injuries for each fatality, with over a challenge in that environment, which was very 4,000 reportable crashes per year (Becker 941). compact. However over the past 50 years ambulance vehicles in the USA have become larger and larger – There has been a limited number of peer reviewed and transitioned from the intact automotive passenger automotive safety engineering tests conducted for the vehicle to the truck chassis with an after market ‘box’ EMS environment in Sweden (Turbell 1980), or a modified van with an aftermarket elevated roof. Australia (Best 1993, Levick 1998), and the USA What should be kept in mind is that these vehicles, (Levick 2000-2001). That which has been conducted related largely to how they are operated, are vehicles has clearly identified some predictable and largely at high risk of crash and thus it would seem prudent preventable hazards, particularly pertaining to that the safety and crashworthiness of these vehicles intersection crashes and the hazards of the rear be optimized. patient compartment, demonstrating the benefit of use of existing restraints for occupants, the How safe are EMS vehicles and to what standards are importance of over the shoulder harnesses for the they designed and tested? Despite the large strides recumbent patient and firmly securing all equipment that the general automotive industry has made in the (Best 1993, Levick 1998-2006). These studies also last 30 years in the safety of passenger vehicles, this identify hostile and hazardous interior surfaces of the expertise has not yet been translated substantively to rear compartment, as well as a need for head the safety of ambulance vehicles. There are few protection. safety standards and no crash safety test procedures or guidelines that provide occupant protection in Many fatal and injurious ambulance crashes occur at ambulance vehicles in the USA. Limited safety intersections – either with the ambulance being struck testing requirements were established in Europe in with a side impact (more likely on its right side) or 1999 (CEN 1789). Australia has had the ambulance frontal impact. Failure to stop at an intersection for restraint standard ASA 4535 in place since 1999, and all vehicles is an extremely high risk practice. Lack it is the most stringent globally (AS/NZS 4535). Thus of use of seatbelts by EMS personnel is cited ascertaining the safety of EMS transport vehicles frequently in the literature as a predominant cause for (and products in that environment in the USA) the high injury and fatality rates for occupants in remains limited largely to sparse expert opinion and EMS crashes (Becker 2003). The hazards resulting peer evaluation, often by non automotive safety from the failure to secure equipment in the patient engineering expertise and in a piecemeal fashion. compartment, which has also been found to cause serious injury in the event of a collision has also been EMS has been generally demonstrated recently to be documented. This is supported by the engineering Levick 2 data from ambulance safety research involving crash landmark vision zero paper (Tingvall 1998). There is tests (Levick 2001), as well as insurance and extensive engineering literature on the principles litigation records. With ambulance crashes being behind crashworthiness and occupant protection. identified in the USA as the highest cause of patient These principles are reviewed in both the Rechnitzer adverse event mortality and serious morbidity (Wang (Rechnitzer 2000) and Grzebieta (Grzebieta 2006) 2007). papers which address these fundamental approaches that underpin