A picture of a sled take a look at simulation utilizing the BioRID-II FE mannequin for LS-DYNA software program in contrast with the IIHS sled and BioRID dummy

By Marcy Edwards
Senior Analysis Engineer, IIHS

The situation isn’t onerous to think about. A driver is stopped in site visitors when instantly one other automobile slams into them from behind. The particular person within the struck automobile — particularly if she’s a lady — is now prone to debilitating neck ache that would intrude with work and life for months to return and result in monumental medical payments.

Although not often life-threatening, neck sprains and strains, which generally happen in rear-end crashes, are essentially the most steadily reported accidents in U.S. auto insurance coverage claims. Because of this, they had been one of many first forms of accidents that IIHS turned its consideration to once we began testing autos for crash safety.

By any measure, our head restraint scores had been a hit. They led to enhancements in seat and head restraint designs which have proven up in real-world crash statistics. However with practically all autos now incomes good scores, our checks now not differentiate amongst autos to encourage additional enchancment. And although the neck damage drawback has lessened, it hasn’t gone away.

My colleagues and I are at present growing a path for the way forward for IIHS rear-impact testing. Our long-term purpose is to have the ability to consider how nicely every mixture of a seat and head restraint protects folks of all completely different configurations and dimensions in quite a lot of seating positions and crash situations. Getting there’s a multistep course of and would require use of digital testing with laptop fashions in addition to the traditional instruments utilized in our authentic head restraint take a look at. We’ll additionally want the assistance of scientists growing detailed laptop fashions of the human physique and the cooperation of auto producers.

How we acquired right here

Once we started score head restraints in 1995, we began with the fundamentals. Neck accidents in rear impacts happen when the top lags behind the accelerating seat and torso. This lag can typically be prevented by good head restraint geometry, so our first evaluations had been easy measurements utilizing a dummy representing a 50^th-percentile man. A restraint ought to be at the least as excessive as the top’s heart of gravity, or about 3½ inches under the highest of the top. The backset, or the gap from the again of the top to the restraint, ought to be as small as potential.

In 1995, solely 3 % of the top restraints we evaluated acquired good geometric scores, whereas 82 % had been rated poor. Our scores led producers to concentrate to those measurements lengthy earlier than a 2010 authorities customary made good geometry a authorized requirement.

Good geometry is important, nevertheless it’s not ample. Seats can differ in different methods too, similar to construction placement, seatback stiffness and energy-absorbing properties, all of which might have an effect on outcomes for occupants.

In 2004 we added a dynamic take a look at for any automobile with or acceptable geometric score to guage how nicely the seat and head restraint managed crash power and occupant movement. This take a look at consisted of a simulated rear influence with the automobile seat mounted to a sled. A particular dummy often known as BioRID, which has a sensible backbone, was buckled within the seat. The heartbeat used within the take a look at was equal to a rear-end crash with a velocity change of 10 mph, or a stationary automobile being struck at 20 mph by a automobile of the identical weight.

The mixture of our geometric scores and our dynamic checks allowed us to determine the simplest head restraints. In a examine of real-world crashes, damage charges had been 15 % decrease for autos with good scores in contrast with these rated poor, whereas long-term accidents, or these lasting three months or extra, had been 35 % decrease.

Past BioRID

Since we started dynamic testing, producers have gotten excellent at designing seats for the ten mph velocity change, and as we speak’s autos all carry out nicely in that take a look at. Nonetheless, there are nonetheless variations in real-world efficiency. Insurance coverage claims knowledge collected by my colleagues on the Freeway Loss Knowledge Institute recommend that damage charges in rear-ended autos with good head restraint scores range extensively.

So how can we design a brand new analysis to higher differentiate amongst restraints?

One comparatively simple replace we intend to make is so as to add a second dynamic take a look at with a bigger velocity change, since many real-world front-to-rear crashes happen at increased speeds. By including a 15 mph take a look at on prime of the ten mph one, we will glean extra data and encourage additional progress. We plan to launch a brand new score program based mostly on the 2 checks inside the subsequent yr or two.

Past take a look at velocity, different variables are more durable to tweak. As is the case with all crash take a look at dummies, BioRID has restricted capabilities — for instance, it’s solely legitimate for fore-aft movement and lower-severity crashes — and doesn’t signify the range of the driving inhabitants. Whereas it’s a formidable software with one thing that intently resembles a human backbone, it represents the particular backbone of a 50^th percentile male.

Actual-world damage knowledge inform us that girls are extra probably than males to endure neck accidents in crashes, however we don’t actually know why. Researchers in Sweden are at present growing a feminine dummy to be used in rear-impact testing, which may sometime assist us consider safety for ladies particularly. Nonetheless, irrespective of how subtle, bodily dummies can’t seize gentle tissue and nerve harm, which can play a job in whiplash accidents and within the variations between males’s and ladies’s susceptibility to them.

Maybe extra importantly, any bodily dummy, male or feminine, represents only one explicit physique sort. Alternatively, laptop fashions of the human physique, that are at present underneath improvement, might be extra simply different to signify a spread of physique varieties and damage danger elements. Digital testing with these fashions may sometime quickly present us with the flexibility to see how seats and head restraints perform for a lot of completely different folks sitting in numerous positions.

The trail ahead

How can we get from bodily checks carried out on precise seats to a a lot wider set of checks carried out just about? One huge problem is that whereas we will exit and buy autos with bodily seats to check, we can not buy laptop fashions of these seats. These fashions are the mental property of the producers, so we’ll want their cooperation. On the similar time, we’ll have to construction this cooperation in order that it doesn’t compromise the independence of the testing program or the belief customers place within the outcomes.

Now we have an extended and profitable historical past of accepting take a look at knowledge from bodily crash checks carried out by automakers for a lot of of our scores. In lots of circumstances, we permit established producers to conduct checks in accordance with our protocols after which provide us with video and different knowledge in order that we will confirm the outcomes and assign scores. We randomly audit these manufacturer-conducted checks by repeating a few of them in our personal facility to ensure the outcomes match up.

We intend to construct on that mannequin as we department out into digital testing.

We’re planning to include digital checks into our head restraint scores in phases. As a primary step, we’ll give producers the choice of submitting digital take a look at knowledge for our new 15 mph take a look at and our established 10 mph take a look at. This part will assist us get accustomed to working with digital take a look at knowledge.

Later, we’ll broaden the variety of required take a look at situations, probably various issues like velocity, seat place and occupant place — for instance, a passenger leaning ahead as a result of onerous braking or a driver wanting down at a telephone of their lap. Our plan is to finally broaden the required digital checks to incorporate situations that may’t be examined in the true world due to the restrictions of the dummies and different instruments we have now. That is the place we’ll be capable of consider efficiency with occupants of various physique varieties and likewise in numerous positions that may’t be achieved by a bodily dummy.

To verify the digital outcomes for all these completely different take a look at situations match actuality, we’ll conduct bodily checks for a few of them. Replicating some outcomes after which making certain the identical seat and dummy or human physique fashions are used all through the digital analysis will assist us validate all the outcomes, together with those for situations we will’t bodily take a look at.

I’m wanting ahead to working with the business to enhance rear-impact safety for a various inhabitants of drivers and passengers with the assistance of digital testing. The street map we’ve laid out will permit us to maneuver into this new territory rigorously and intentionally. And as we be taught from this primary expertise, we’ll be capable of apply this information to different crash varieties, probably spurring a wide selection of auto security enhancements.

SOURCE: IIHS