Underride Crash

General Questions related to the CRASH Program and clones
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brian
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Joined: Tue Jul 14, 2009 10:52 am

Underride Crash

Post by brian »

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Q: I have a situation where a pickup struck the side of a semi trailer between the landing gear and the trailer's wheels. The trailer was at a 30 degree angle to the pickup and the pickup skidded straight into the collision. Any information on this type of damage?
A: NOTE: In an angled underride crashes, not all the energy goes into the vehicle crush. A significant amount of energy may be dissipated as the vehicle moves and slides and gouges subsequent to the initial impact. I would suggest brushing up on some of the concepts of Energy Correction Factor(ECF). Be sure to also check the NHTSA crash test database.
  • There are many angled barrier crash tests whcih are included in the database. McHenry Software Users, from medit32, simply select Databases->NHTSA Databases w/Extended data
The following are 2 papers on underride collisions.
  • Struble, Welsh & Struble "Crush Energy Assessment in Frontal Underride/Override Crashes”,SAE Paper 2009-01-0105
    • Abstract: Compatibility or aggressivity between vehicles in frontal crashes can be manifested by differences in the ways that upper and lower structures deform, when compared to each other, or when compared to the deformation modes in full-width impacts into rigid barriers. Flat barrier tests are very useful for characterizing the structure and determining the crush energy, and are indeed the underpinning of existing reconstruction methods. However, conventional methods can be problematic when flat barrier test data are applied to underride/override crashes. Useful insights in grappling with such situations were obtained by analyzing a series of NHTSA-sponsored crash tests into full-width rigid barriers, in which advanced measurement protocols were employed. Dynamic force-deflection characteristics were developed, and absorbed energies were calculated, for the upper and lower structures of the tested vehicles. Distinct CRASH III-type models were developed for these structures. For all the other crash test data not employing advanced measurement protocols, a means was developed for approximating the crush energy contributions from the upper and lower structures, based on data from full-width rigid barrier impacts. To test its validity for under/override crashes, the method was applied to published crash test data for some repeated frontal impacts into an overhanging barrier. Good predictions of the crush energy were obtained. The paper contains recommendations for future measurement protocols, and how to use the developed procedures for vehicles not tested according to improved protocols.
    • Limitations “The proposed underride/override model has been validated against a very narrow range of vehicles only. It should be tested against other staged underride/override crashes as they become available.”
  • Another paper is by Trego, et al "A Scientific Approach to Tractor-Trailer Underride Analysis", SAE Paper 2003-01-0178
    • Abstract: Crashes between passenger vehicles and large tractor trailer vehicles often result in serious injuries and death. There have been few studies of this class of crash involving the side of the large tractor trailers and the passenger vehicles. Studies have shown that side underrides are underreported in crash records. A literature search has shown that there are no generally accepted methodologies to document and scientifically reconstruct a side underride accident. Some of the problems existed because there was a general lack of information on the side underride crash. Rear underride crashes were being studied which yielded helpful information. This led the authors to study a series of trailer side underride crashes that were performed to determine if there were sufficient relationships between passenger vehicle body and roof styles and the side of large highway trailers to allow the development of a general formula for underride impact speed analysis of a vehicle where the roof and roof support structure of the vehicle was damaged. These tests provided valuable insight into the relationships between passenger vehicle roof structures and the sides of large box trailers.
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brian
Posts: 499
Joined: Tue Jul 14, 2009 10:52 am

Re: Underride Crash

Post by brian »

Found and uploaded to the website another report of interest for underride crashes:
  • DOT HS 808 231,Final Report,June 1993, Final Report of a 1990 Ford Taurus into Heavy Truck Rigid Rear Underride Guard in Support of CRASH3 Damage Algorithm Reformulation (7 megs)
    • PURPOSE AND TEST PROCEDURE
      The purpose of the four (4) heavy truck rig id rear underride guard impact. tests was for research and development in support of the CRASH3
      damage algorithm reformulation. The 1990 Ford Taurus was equipped with a 3.0-liter, 6-cylinder, transverse, gasoline engine with a 3-speed automatic transmission. The test weight of the vehicle was 3331 pounds. The vehicle was instrumented with six (6) accelerometers to measure vehicle X-axis and Y-axis acceleration.Each crash test event was recorded by two (2) high-speed motion picture cameras operating at approximately 1000 frames per second.
Please also see Review of CRASH damage analysis and the NHTSA "reformulation"
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Chris G

Re: Underride Crash

Post by Chris G »

Recent paper on Underride announcent in Accident Analysis & Prevention
Volume 42, Issue 1, Pages 1-346 (January 2010)
  • Experimental evaluation of underride analysis techniques and empirical validation of a new analytical technique, Boggessa,Morrb,Petermanb and Wiechel
    • AbstractAccident reconstructionists are often faced with damage patterns and locations on vehicles that are not well defined by available barrier impact data. One such example is a frontal underride collision. Underride impacts occur when there is a height mismatch between the primary structural components of the impacting vehicles, and the vehicle with the lower height is forced beneath the structure of the other vehicle. The lack of structural engagement typically allows for significantly different damage patterns due to the inherently lower stiffness of the underriding vehicle's contacting surfaces coupled with complex interactions between varying surfaces. In this study, a series of two-vehicle impact tests between a small pickup (bullet vehicle) and a large dump truck (target vehicle) were performed and studied. These tests involved a severe underride configuration in which the dump truck bed's vertical alignment was above the base of the windshield of the pickup. Coupled with these impacting surfaces was a single vertical support, a remnant of a commonly referred to ICC (Interstate Commerce Commission) bumper, which caused a narrow object-type impact, but did not extend down to the pickup's bumper. Multiple prior authors’ analytical and empirical relationships to predict impact speed based on crush damage were evaluated using the results of these tests as well as other published underride tests. No single model was sufficient at predicting the mixed mode of impact present in these impact scenarios. However, a system of equations was developed to predict the impact parameters utilizing a combination of previously reported methods and a new empirical relationship presented in this study. This new method shows high correlation and supports the authors’ hypothesis that separate crush models can be applied to multiple discrete areas of a vehicle and then combined to form a more complete predictive systematic model.
MSI
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Re: Underride Crash

Post by MSI »

on another forum a few other citations recently cited
Crush Energy Considerations in Override/Underride Impacts SAE 2002-01-0556
ABSTRACT:
  • In automobile accident reconstruction it is often necessary to quantify the energy dissipated through plastic deformation of vehicle structures. For collisions involving the front structures of accident vehicles, data from Federal Motor Vehicle Safety Standard (FMVSS) 208 and New Car Assessment Program (NCAP) frontal barrier impact tests have been used to derive stiffness coefficients for use in crush energy calculations. These coefficients are commonly applied to the residual crush profile of the front bumper in real-world traffic accidents. This has been accepted as a reasonable approach, especially if there has been significant involvement of the front bumper and its supporting structures. For impacts where the structures above the bumper level are deformed more than the bumper itself, this approach may not be so readily applied. These types of impacts are called override/underride, and are encountered quite often in truck-to-car accidents where there is a vertical difference in bumper heights and also in accidents where bumper height mismatches are created through vehicle brake dive. In this paper we examine the crush-energy considerations of override/underride impacts. The limited available literature and test data are reviewed. Two test programs that involved impacts over a wide range of severities are analyzed in detail.
Here's an underride crash test at IIHS

and a section on IIHS Recognizing good rear underride protection


Here are links to the crashes: SATAI 2012
Test 1 into end of trailer at 10

Test 2 into side of trailer at 25

Test 3 into end of trailer at 35
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