Urgent Underride Discussion of Deceleration Forces/High Speeds. Don’t Dawdle.

While I was indeed encouraged by the incredible interaction and communication at the Underride Roundtable, I am well aware of just how much still needs to happen in order to make trucks safe to drive around.

View the entire event here: https://event.webcasts.com/starthere.jsp?ei=1100569

Media Coverage of the first Truck Underride Roundtable held at IIHS on May 5, 2016

I summarized some of my initial reactions here: 4 out of 8 Major Trailer Manufacturers Have Passed All IIHS Tests; Where do we go from here?

I’d like to address the urgent need for progress to be made promptly to improve underride protection, specifically to design and crash test for higher speeds than 35 mph. I asked about it at least two times during the Roundtable. And, at one point, someone from the trucking industry raised the concern about deceleration forces causing injury at higher speeds.

This is an issue which pushes my button — especially because I have heard over and over that prevention of underride is possible at higher speeds — and I have written about it in the past:

The Truck Trailer Manufacturers Association Reaction to IIHS Report: What is the Truth?

Setting the Record Straight: “Too Rigid” Underride Guards is a Myth

It was bothering me after the Underride Roundtable because of the simple fact that misunderstanding of this issue could be a major obstacle to NHTSA requiring and the industry voluntarily producing stronger underride guards.

So, I emailed some people about my concern over this issue. (No, not me!) This is what I wrote to them:

I would like cleared up, once and for all, the misconception — if it is one — that deceleration forces would cause unintended injuries if the guards were made too strong. It pushes my button when I hear someone authoritatively say it — when I’m not sure that they are basing it on anything other than hearsay. I appreciated what Aaron Kiefer said in response to the comment made at the Roundtable about this and I would like it addressed so that it does not remain as one of the obstacles to more effective protection.

I had asked several people in the public health/injury prevention fields to attend but mostly they thought that underride was not their area of expertise. I, on the other hand, am convinced that we need the public health/medical people providing input. 

As I have said many times, what people in the industry are saying does not make sense to me on many levels, including the fact that I survived a horrific truck crash and did so, as far as I am concerned, because I did not experience PCI/underride myself. I had many months of limping and leg cramps at night and painful neck and back tension probably due to whiplash and traumatic muscle memory. But that is all gone now and physically I am in great shape.


Here are some emails which I received in reply to my search for the truth of this matter:

From Raphael Grzebieta, Australia, who has worked to upgrade the Australian/New Zealand underride standards:

George and I heard that BS statement from car manufacturers (in particular, from a prominent engineer who was head of Australia’s Commodore vehicle design team) more than two decades ago when we were highlighting the appalling crashworthiness of the Australian family sedan vehicle the Holden, mainly  because of strength deficiencies and weaknesses (poor spot welding, etc.) of the structure surrounding the occupants. This GM-Holdens engineer’s argument was back then: make them too strong and you wind up killing people inside because of the large inertia forces. He claimed structural components have got to be weaker to crush and crumple to absorb energy and make the vehicle decelerate at a lower rate – it’s an old defence tactic used by manufacturers to obfuscate crashworthiness design flaws. The trouble with his position was that they made them so weak it killed people because of massive intrusion into the occupant space.

Well, the more ethically responsible companies such as Mercedes and Volvo along with the NCAPS around the world and IIHS has proven, with all of their excellent work and testing, that this is a completely false assumption. It also violates the crashworthiness principles set down by De Haven almost half a century ago.

De Haven’s principles are:

  1. The package should not open up and spill its content and should not collapse under expected conditions of force and thereby expose objects inside to damage,
  1. Packaging structures which shield the inner container must not be made of brittle or frail materials; they should resist force by yielding and absorbing energy applied to the outer container so as to cushion and distribute the impact forces and thereby protect the inner container,
  1. Articles contained in the package should be held and immobilised inside the outer structure, and
  2. Wadding, blocks or means for holding an object inside a shipping container must transmit the forces applied to the container to the strongest parts of the contained objects.

(see https://www.researchgate.net/publication/254791228_Rollover_Crash_safety_Characteristics_and_issues, where we discuss De Haven’s principles concerning Rollover Crashworthiness – another ‘wicked problem’ in crashworthiness not unlike the under-ride problem in terms of poor regulations and manufacturer’s resistance to change)

The principles of our Australian AS3845–Part 2 standard relating to underrun barriers are:

  1. Ensure there is a good crashworthiness interface (flat surface that is not far off the ground – see ‘Interface Compatibility’: https://www.researchgate.net/publication/242129393_Crashworthy_systems-_a_paradigm_shift_in_road_safety_design and ‘Incompatible Vehicle Systems’ https://www.researchgate.net/publication/237219017_Crashworthy_systems_-_a_paradigm_shift_in_road_design_part_II ) between the vehicle crashing into the back of the truck and the truck’s rear end (no spears or guillotines) that is capable of sustaining the crash forces generated (25 to 35 tons depending on speed).
  1. Use the car (the package) with crumple zones, restraints and seat belts (wadding, blocks and means for holding the object {human}) as the device that dissipates the kinetic energy of the vehicle crashing into the back of the truck. IIHS and NCAP tests have already ensured the occupant compartment (the cocoon) does not fail structurally so long as there are no line loading (guillotine effect) from the rear tray above the front sill level ( no lateral loads applied to the green house portion of the roof structure). Crumple zones outside the cocoon protecting the occupants, along with the restraints and airbags within the cocoon, provide the required deceleration ride down for the occupants to survive the crash. However, if the under ride barrier is not strong enough to withhold the crash loads, and the interface collapses, we get serious intrusion into the occupant cocoon survival space.  

So, in summary, what [the industry] is saying is simply plain wrong and tell him so from us, the world experts down under!

TTMA are still stuck back in the dark ages pre start-up of NCAP and IIHS crash testing facilities and rating days, spreading unfounded mythology like other manufacturers did in those olden days. It will cost them dearly if they try that argument on in a defect law suit.

They should simply suck it up and start redesigning the truck under run barriers to be crashworthy. One can design an energy absorbing underride barrier but that takes a lot of design effort. It also must restrict the stroke to a certain limit so that the rear tray does not intrude into the occupant cocoon survival space. Probably a lot of effort for little gain. 

Dynamic crash testing along the lines of what IIHS have done and what we are proposing is essential.


And here is a response to my question from Jared Bryson, advisor to the Virginia Tech engineering students who took on underride for their senior research project:


I found that comments at the end of the round table did not sit particularly well with me.  Allow me voice my thoughts, in two directions.

G loading:

1)      In a deceleration (single axis , eyes-out) a typical individual can sustain an incredible g load over short durations.  Military and Aviation have a wealth of information in this respect (Einband and Wikipedia images shown below). 

2)      Typical impacts are sub-one second.  As a more cited example, the IIHS Belair v. Malibu appears to be in the neighborhood of 150 ms duration. 

3)      In a linear model, stopping from 50mph in 3 ft (less than 1/10 second) should generate 28 G.  30 G is survivable in this timeframe.  Bear in mind reality is not linear, but a model below injury threshold is a good starting point.   

Survivable speeds:

1)    Extrapolating from Matt’s presentation: The old Vangaurd passed 100% @35 mph.  In the buck test, Wabash can withstand 33% more force and absorb more energy.  The Wabash should be able to withstand a 38 mph impact.  Not much of a design stretch for 40 mph.

2)   Robert Mazurowski’s presentation showed a mean of 44 mph in rear underride for trailers and SUTs (Slide 12).

3)    IIHS’s 50th anniversary showed the wonderful advance in light vehicle safety systems between 1959 and 2009, at 40 mph.   


Jared Bryson chart 2 chart from Jared Bryson

When I asked Jared to summarize his thoughts, this is what he shared with me:


Manac, Wabash, Vanguard, and Stoughton each offer a partial overlap capable design that is well received by industry. 

This industry shift in underride design combines improved structure with features facilitating safety systems in modern passenger vehicles. 

There is evidence these new designs are not only viable at higher speeds, but survivable

Please feel free to disseminate any of our conversations.

Last night, I was mulling over some other comments from the roundtable.

Stopping with the engine block:

1)      For decades, automobile design has intended for the engine block to eject below the passenger cabin in a severe frontal impact.  This is to prevent engine PCI.

2)      Limiting underride is imperative, as underride can limit this engine ejection vector.

3)      Not impacting the bumper structure bypasses the active safety systems found in modern vehicles (airbags, pre-tensioners, energy absorbing crumple zones).  This translates to more severe loading for occupants.

Stopping a car with the A-pillars:

1)      The short deceleration distance would create a fatal g load.

2)      Structure to sustain this type of loading would require a radical new approach to automotive design.

3)      Again, not impacting the bumper structure bypasses the active safety systems found in modern vehicles…


I raised my hand countless times to ask a question at the Roundtable. Push, push, push. . . challenge, question. Surely there are some who think that I am a thorn in their side.

But when it comes right down to it, most of those tasked with the responsibility of doing something about the underride problem (thankfully) do not have that inner voice reminding them that every ounce of patience with the status quo, every moment of pausing to be thankful for that bit of progress which has been made, is torture because it feels like a compromise is being made to stop forward momentum–thus giving up on the Best Possible Protection and sacrificing the life of yet one more underride victim as the Crash Death Clock continues to tick. Tick. Tock. Tick. Tock.

Yes, a lot of work needs to be done by many parties involved in this process. But if we were all to wait another year for another Roundtable (or for a new rule to be issued) before moving ahead with working diligently on this problem, that would be hundreds of more people sacrificed for no good reason. And we’ve had enough of that for too many years.

Just ask those who have already lost a loved one because of misconceptions or outright resistance. I’m sure they might tell you, “Please don’t dawdle. Preventing underride is an urgent matter!”


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