AAAM’s 53rd Annual Conference: Highlights of Day Two and Three
The Association for the Advancement of Automotive Medicine (AAAM) held its 53rd Annual Conference in Baltimore, Maryland from October 4th through October 7th, 2009. Highlights of Tuesday and Wednesday sessions included: a special session on Pre-Crash Technology moderated by Jim Fell of the Pacific Institute for Research and Evaluation (PIRE), a keynote speech by Dr. Thomas M. Scalea, MD, FACS Physician-in-Chief of the University of Maryland R. Adam Cowley Shock Trauma Center and a presentation by Ted Miller, Ph.D. from PIRE titled Cost of Crashes Related to Road Conditions.
The special session on pre-crash technology included the presentations:
- An Overview of NHTSA Research on Advanced Crash Avoidance Technologies by Ray Resendes Chief, Intelligent Technologies Research, National Highway Traffic Safety Administration (NHTSA) included an interesting reference to General Motors’ 1939 World Fair Exhibit which is described by a two-part You Tube video. The substance of the presentation listed an array of state of the art technology including: Electronic Stability Control (ESC, 100% phase-in pursuant to FMVSS126 by 2012), adaptive cruise control (first in Japan in 1998), forward collision warning, forward collision avoidance and mitigation (set for a 2011 rulemaking decision), blind spot detection, lane departure warning, lane departure prevention (set for a 2001 rulemaking decision), crossing path detection (a backup sensor), fatigue detection, night vision assistance (around for about 10-years), automatic alcohol detection, crash notification and vehicle to vehicle communication (set for rulemaking decision in 2013).
- The Latest in Crash Avoidance Vehicle Technology by Brian Fildes, PhD, Associate Director, Monash University Accident Research Centre – Europe, Prato, Italy presented results of the TRACE Report, a 2007 European project that identified 140 new safety technologies. Dr. Fields noted that it was possible that the report was already obsolete given the pace of commercial implementation and technological development of pre-crash technologies.
- Crash Avoidance Technologies – Acceptance and Early Estimates of Effects by Adrian Lund, PhD, President, Insurance Institute for Highway Safety (IIHS) began his presentation with a summation of 50 years of crashworthiness improvement showing the IIHS recent test of a 1959 Chevrolet Bel Air and a 2009 Chevrolet Malibu in a 40 mph frontal offset crash test. The test is a reflection of how improving the compartment has improved motor vehicle safety. Dr. Lund made a special note that motorcycle Anti-Lock Brake Systems (ABS) appears to reduce the chance of a fatal motorcycle crash by 30%; he noted that motorcycle ABS is like ESC for cars. The bulk of the presentation dealt with the IIHS analysis of driver perception and acceptance of Volvo’s pre-crash technologies; noteing that it appeared that most people seemed to like the prevention systems they had in their Volvo cars.
Dr Thomas M. Scalea keynote speech provided a compelling argument for the kind of trauma system used in Maryland. Examples were provided that illustrated treatment improvements that occurred because of the trauma system concentrates critical injuries at level 1 trauma centers. Dr Scalea’s talk was titled From Trauma Centers to Trauma Systems. The Maryland program encompasses 70 physicians from seven different academic departments in the University of Maryland, Baltimore. The nearly 100 bed trauma hospital employs over 300 nurses and a total staff of 450 people. This year the shock trauma will admit over 7700 patients.
Ted Millers presentation of the paper he co-authored with Eduard Zaloshnja, Ph.D was titled Cost of Crashes Related to Road Conditions, United States, 2006. According to the abstract the paper is the first study to estimate the cost of crashes related to road conditions in the U.S. The study used 2000-03 Large Truck Crash Causation Study (LTCCS) data and applied logistic regression results to calculate the probability that road conditions contributed to the involvement of a vehicle in each crash. Dr Miller indicated that the estimated comprehensive cost of traffic crashes where road conditions contributed to crash occurrence or severity was $217.5 billion in 2006 and concludes with the observation that road conditions are largely controllable and that road maintenance and upgrading can prevent crashes and reduce injury severity. The study is particularly interesting in light of recent emphasis of the car as the nexus of pre-crash intervention technology. Elimination of crashes will require the proper emphasis of driver, environment and vehicles and the present study underlines the importance of the driving environment in the crash prevention matrix.
AAAM’s 53rd Annual Conference: First Day Highlights
The Association for the Advancement of Automotive Medicine (AAAM) is holding its 53rd Annual Conference in Baltimore, Maryland from October 4th through October 7th, 2009. The conference is well attended by over 130 participants.
Highlights of Monday’s morning sessions included: a presentation by Jason Hallman from the Medical College of Wisconsin titled Splenic Trauma as an Adverse Effect of Torso-Protecting Side Airbags: Biomedical and Case Evidence and a presentation by Dr. Jo Barnes of the Vehicle Safety Research Centre, Ergonomics and Safety Research Institute, Loughborough University, titled Comparison of Injury Severity Between AIS 2005 and AIS 90 in Large Injury Database.
The paper on splenic trauma described cases involving zero interior intrusion in near side impacts (one case had minimal interior intrusion) in which a seat mounted side airbag deployed and significant splenic injury occurred. Follow-up experiments using a test fixture, deploying seat based side airbag and out of position cadaver illuminated possible injury mechanisms. Overall it appears that splenic injuries in minor side impact crashes may occur from seat mounted airbag deployment when injury would be unlikely to otherwise occur. One point made in the discussion was that the larger seat mounted side airbags, designed to cover both the torso and head, appear to have been involved in most of the cases presented and that the vehicle fleet’s use of seat mounted side impact airbags is tending toward a smaller torso only bag with head protection provided by side curtain.
The paper presented by Dr. Barnes showed detailed differences in severity grading between the AIS 90 and AIS 2005. In general AIS 2005 was shown to produce lower counts of AIS 3 and AIS 4 injuries using an identical data set. In other words, a distribution of injury severity when coded with AIS 2005 will be lower compared to an identical population coded with AIS 90. The implications of such a difference are significant – particularly since the National Highway Traffic Safety Administration has recently adopted the AIS 2005 and new NASS CDS coding will be using AIS 2005. Greatest differences were described for the thorax, head and extremities body regions. Anyone who is using AIS coding needs to be careful to check what version current injury coding is based upon and remember that the historical AIS coding is based upon AIS 90 and in some cases earlier versions.
According to the Chairman of the AAAM Scientific Program Committee, Clay Gabler of the Center for Injury Biomechanics, there are 23 papers being presented at the conference, including 6 student papers. One paper is made through an international scholar award and two student papers are funded with endowment grants. The conference includes 14 posters and two special sessions. Special session topics include: Technology and Treatment Addressing Medical Fitness to Drive and Pre-Crash Technologies.
Will Electronic Stability Control Eliminate Tire Tread Separation Crashes?
By Mark Arndt
Will Electronic Stability Control Eliminate Tire Tread Separation Crashes?
Probably not, but the technology holds great promise to substantially reduce these crashes. Recently published testing results demonstrate that Electronic Stability Control (ESC) systems provide drivers a greater steering margin of safety when their vehicle experience a rear tire tread separation.
The study also found that not all ESC systems are alike in their potential benefit. Some systems provide a greater benefit to the driver in the event of a rear tire tread separation than others.
A rear tire tread separation event can lead to loss of vehicle control as a result of an unexpected deviation to the vehicle’s intended path in combination with significant change that occurs to the vehicle’s steering characteristics. Vehicle designers have had difficulty providing substantial improvements in basic vehicle response after a tire tread separation, but ESC was shown to make a substantial improvement in rear tire failure events (video).
Fuel Fill Pipe Damage, Leakage and Fire by Tire Tread Separation
Filed under: Fill Pipe, Fuel Tank, Testing, Tread Separation
By Mark Arndt
Given knowledge of the dangers, the notion that tire failures occur on vehicles traveling at highway speeds is frightening. Yet, such failures occur and the general acceptance of tire failure is so deeply rooted in vehicle performance that spare tires are standard equipment.
A specific rollover incident in which a rear tire tread separation caused tearing apart of a fuel tank fill pipe routed just behind the wheel well was recreated in a controlled test (watch video). The incident resulted in fuel spillage, fire and burn injuries. The October 2001 incident involved a 1995 Land Rover Discovery with a General AmeriStar tire failure. The vehicle manufacture’s corporate representatives were shown the test in late 2002 during depositions.
High speed video captured contact between tire tread and reinforced rubber fuel hose as the flailing end of the tread separates from the tire. Repeated contacts by the tread to the fill pipe fuel hose and vehicle underbody result in fill pipe failure and release of liquid from the fuel tank. Tests of a peer vehicle did not produce a failure or leakage.
Regarding vehicle handling and tire tread separation, failures a relationship between vehicle design and loss of control is scientifically documented. Only recently has an incremental improvement in vehicle handling following tire tread separation been demonstrated with Electronic Stability Control (ESC). Regarding other aspects of vehicle performance in tire failures, specifically including tire tread separations, dangers exist that can enhance the chance of harm.
It is a well know consequence of tire failures that the tire tread can damage the vehicle. In tire tread separations substantial damage to the wheel well sheet metal is probable. Tire tread failure induced damage has been documented to hydraulic brake lines, parking brake cables, tail lights, fuel fill pipes, wiring and bumpers. Parts of a car, not to mention the tire tread, can be knocked free and onto the road surface. Vibrations from a tire failure have tripped inertially activated fuel pump cut off switches resulting in unexpected engine cut-off.
Engineers can readily foresee similar scenarios for a variety of safety equipment that is taken for granted in motor vehicles. For example:
- A tire tread separation occurs at night, damages wiring that routes near the wheel well and renders driver’s suddenly blind to the road or hazards on the road,
- A tread separation causes permanent damage to hydraulic brake lines or parking brake cables resulting in brake failure or compromised performance.
- A tread separation causes damage to a light cover or reflector, often rear taillight breakage is observed.
That these are important events in a vehicle’s safety performance is simply supported by the fact that Federal Motor Vehicle Safety Standards (FMVSS) regulate the performance of vehicle systems that are directly dependent upon the key components described above.
A tire failure event could be analogous to the Part 581 Bumper Standard. Low speed, often parking related, bumper contacts occur in normal driving. Comparatively, tire failures are also expected – driving manuals instruct how to react to a tire failure and most cars have spare tires. Anticipating low speed contacts, the Part 582 Bumper Standard covering all passenger motor vehicles sold in the United States prescribes protective criteria for: lamps, reflective devices and head light alignment; operation of doors; fueling and cooling systems; propulsion, suspension, steering and braking systems; impact energy absorbers; fasteners and joints; and, even separations of surface material, paints and coatings and permanent deviations of original contours. Comparatively, following a tire failure a vehicle should be capable of performing at the minimum level of safety prescribed by applicable FMVSS. Vehicle design interventions can effectively eliminate dangers from tire failures induced vehicle component damage.
New Test Results: A Breakthrough in Understanding Front Tire Failure Crashes
Filed under: Crash Reconstruction, Random, Testing, Tread Separation
By Mark Arndt
Not all tire tread separations are equal and new testing documents previously unknown differences between a front tire failure and a rear tire failure. Almost universally, tread separation event testing is limited to rear tire failures. Most of the Ford Explorer/Firestone Tire crashes involved rear tires and the causes of these crashes are attributed to a variety of vehicle factors – the largest factor relates to adverse changes in vehicle controllability.
So why do vehicles that have front tire tread separations get into crashes?
The answer, in part, is explained because despite decreased sensitivity to steering the failure event is startling, produces violent vibration and loud noise and pulling. Pulling is turning of the vehicle without the driver turning the steering wheel. Of course, the vehicle steering characteristics also changed suddenly and nonsymmetrically, complicating the driving task. New testing of front tire tread separation demonstates for some vehicles a substantially increased pulling response comparable to equivalent rear tire failure. New testing also documents a torque response transmitted through the steering wheel that may jerk the steering wheel from the driver’s grip.
As a rule of thumb, when a rear tire experiences a tread separation the resulting change in the vehicle’s understeer gradient, a key measure of the vehicle turning characteristics, is roughly three degrees per G (3 deg/G) . Where, G is equal to the acceleration of gravity. And, when a rear tire experiences a tread separation event all vehicles ever tested respond in dynamic maneuvers with oversteer – in other words, they spin-out.
It is perplexing that the same changes at the tire that makes a vehicle spin-out when there is a rear tire failure also makes a vehicle less likely to spin-out when there is a front tire failure – in other words, when there is a front tire failure the vehicle will understeer more and become less sensitive to steering. The new testing results show that an external disturbance may play a greater role that previously understood.
Fuel Tank Fill Pipe Valve Prevents Leakage in Crash
A recent crash test conducted by the San Francisco Law Firm Lieff Cabraser Heimann & Bernstein (under the direction of Transportation Safety Technologies, Inc.) has provided an important measure of the feasibility and performance of fuel tank fill pipe valves in crash situations when the fill pipe is severed or damaged.
The valve positioned inside the fuel tank at the end of the fuel tank fill pipe was part of the Onboard Refueling Vapor Recovery (ORVR) system. ORVR was a safety feature first dictated for passenger cars in 1998 by the US Environmental Protection Agency (EPA) to limit fuel emissions. The ORVR required that fuel vapor generated during vehicle refueling be stored on the vehicle instead of at the gas station. Stored refueling vapors are burned in the vehicle engine after refueling.
A common feature of ORVR systems are mechanism that minimize fuel atomization as it enters the fuel tank and limits to migration of vapors out of the tank when the fuel cap is off. Most manufactures utilize a one way valve on the fuel tank fill pipe. The valve is located either in the fuel tank or in-line of the fill pipe. Some vehicle manufactures have utilized valves that serve a dual purpose of vapor barrier for ORVR and liquid fuel barrier for crashworthiness. The dual purpose valve is a preferred and logical choice given the vulnerability of some fuel tank fill pipes and fuel caps in crashed. Sport Utility Vehicles with their high rates of rollovers are natural benefactors of valves that prevent spilled gasoline from fuel tank fill pipes.
The crash test involved a 2001 Kia Sportage with a modified rear suspension and fuel tank shield. The vehicle was stuck by a Federal Motor Vehicle Safety Standard 214/311R (FMVSS214/301R) moving deformable barrier ballasted to 5011 pounds. The Sportage fuel tank was filled to 15.4 gallons which is about 92 percent of its refill capacity. The Sportage was hit squarely at the rear with the left edge of the barrier aligned 16.5 inches to the right of the Sportage centerline – a right offset rear impact.
As a result of the crash the modified rear suspension posed no threat of puncture to the fuel tank and the fuel tank shield worked. There were no punctures of the fuel tank, but there was a separation of the fuel tank fill pipe. A reinforced rubber interconnecting fill pipe hose tore apart in the crash. The fill pipe failure was observable only as the fuel tank was removed. A static rollover conducted after the crash test pursuant to the rollover test requirement s of FMVSS301 demonstrated no fuel leakage from any portion of the fuel tank – proof that the one way flow valve in the fuel tank fill pipe worked.
Black Box Proven Accurate and Valuable to Crash Reconstruction
By Mark Arndt
A paper recently published at the 2009 SAE World Congress demonstrates the accuracy and utility of speed data collected by the Powertrain Control Module (PCM) of late model Ford vehicles. Testing described in the paper was completed in conjunction with an evaluation of Electronic Stability Control (ESC) systems supported by Tab Turner of the law firm Turner & Associates.
An instrumented 2005 Ford Explorer was used to evaluate speed data provided from its PCM at high slip angles and other dynamic maneuvers. The slip angle is the angle between the heading of a vehicle and its velocity direction –- a vehicle that is side-slipping or spinning out has a high slip angle.
PCM speed was compared to speed and slip angle collected from a calibrated velocity sensor. In addition to speed, slip angle and other standard handling test measurements the vehicle brake switch and throttle were recorded so PCM data could be synchronized. After each test run the vehicle ignition was turned off and the PCM was downloaded using commercially available Bosch hardware and software. The principal maneuver was the National Highway Traffic Safety Administration (NHTSA) sine-with-dwell test consisting of a 0.7 HZ sinusoidal steer with a 0.5 second dwell at the steer reversal peak.
Runs were conducted with the vehicle’s Electronic Stability Control (ESC) disengaged so that the test vehicle would achieve large slip angles. Other dynamic maneuvers included: NHTSA’s sine-with-dwell with ESC engaged; 100% accelerator to 80 mph with 0.5G braking to stop; and acceleration to 50 mph with maximum ABS braking to stop.
Results demonstrate agreement between the speed recorded by the calibrated instrumentation and speed recorded by the vehicle’s PCM for conditions when the vehicle slip angle and rear wheel slip were near zero. PCM speed was lower than instrumented speed in high slip angle maneuvers. PCM on average underreported during maximum ABS braking and at medium to high speed in 0.5G braking. In acceleration the PCM speed had no detectable under-reporting error except at the highest speeds with 100% accelerator application.
Tread Separation: More Than a Gust of Wind
By Mark Arndt
An expert made a statement about tire detreading. He said, “The vehicle gets pulled left only about a foot, in an orientation of one to two degrees, like a gust of wind.” His answer implied there was little danger and as evidence he referred to a paper I had written. Attorney Mikal Watts of the Texas law firm, Watts Guerra Craft asked what I thought about the response given the extensive amount of research and testing our company has done on this topic.
Stated simply, the statement is wrong in its content and it is wrong in it’s context. The current state of knowledge on the consequences of tire tread separation events (tire detreads) is substantially greater than indicated.
First, when tires fail they fail in a variety of ways creating a broad distribution of response that depend upon the nature of the tread separation, the vehicle and the driving environment. In other words, there is not just one type of tire failure and there isn’t just one response associated with tire failures.
Having stated above, one question might be – which paper supposedly describes his response, “like a gust of wind?” The answer is none. In fact, a tread separation event is always described as including vibration, noise and turning of the vehicle and the event has associated adverse changes in vehicle handling. Not even a gust of wind has vibration and pulling. And, the associated adverse change in vehicle handling makes any vehicle dangerous. Driving at highway speeds with a detreaded tire and gusty wind substantially magnifies the danger and chances of a crash.
The numerous papers (1999, 2000, 2001, 2004, 2006, 2006, 2009) I have written on tread separation demonstrate by scientific methods that all tire tread separations cause violent vibration of the tire/wheel and perceptible yet unspecific vibrations of the vehicle. Tire tread separations cause sudden and startling loud noise or noises from the separating tread hitting portions of the car and ground. Tire tread separations cause an external pulling of the vehicle — in other words the vehicle turns without the driver turning the steering (hand) wheel. Pulling could be minor or could force a vehicle off the road. Finally, steering characteristics are degraded and in incidents involving rear tires a vehicle oversteer characteristic results.
TSTi on CBS with Dan Rather
CBS News with Dan Rather featuring Mark Arndt
Mark Arndt on CBS News
Welcome to the Transport Safety Technologies Blog!
This web log is dedicated to discussions concerning public safety. My belief and, by extension, my work is focused on accident prevention and transportation safety. The best way to prevent injury is to prevent the accident.
Building vehicles with protective guards is not as good as building vehicles with preventive guards. I believe more time, attention, and education spent on designing and building vehicles that act and/or react in a way that prevents harm to its occupants is ideal.
Mark W. Arndt
