Text: No. 7 - Song
Recently, many self-media have launched a new crash test comparable to a "chest broken boulder" - the rear-end semi-trailer test, also known as the "car collision trailer" test. The scene is quite thrilling, the content is quite exciting, so that the famous 25% of small offset collisions have to be avoided.
However, 25% of small offset collisions are such a representative and rigorous collision index after a lot of statistics and professional analysis. And now the "car crashing into the trailer" test initiated by the people, is it a lively one, or is it really representative?
25% of offset collisions originated in the IIHS in North America, and the reason for this smaller overlap area collision is the leading cause of fatality in accidents with higher fatalities. Compared with the car crashing into the trailer, the damage of the 25% small offset collision is not so serious, which shows how dangerous the car crash is.
Does the privately-initiated rear-end half-trailer test make sense?
Let's start with the data.
According to the data of recent years of in-depth investigation of traffic accidents in China, the fatality rate caused by rear-end collisions of passenger cars is 2.88%; When a passenger car rear-ended a semi-trailer, the fatality rate soared all the way to 26.74%.
In addition, there is another important information point for these injuries - the speed of most collisions is not fast, and even the relative speed below 50 km/h accounts for more than 60%, but the accident casualties are still large.
Among them, the most lethal collision method is undoubtedly "decapitated killing".
The so-called decapitation refers to the extreme situation that the front of the passenger car is completely "inserted" into the bottom of the trailer, resulting in the A-pillar being cut off. Once the A-pillar can't resist, it means that the occupants in the car are likely to be "killed by decapitation".
This kind of damage is not only extremely lethal, but also extremely visually impactful.
Because the A-pillar is actually the "Achilles heel", the key reinforcement parts are at the corners of the upper and lower ends, but when the rear-end trailer is rear-ended, it can always accurately hit the weak point in the middle of the A-pillar.
Compared with the general impact, the front of the car is hit first, and the impact force is transmitted to the A-pillar, and the A-pillar is compressed. However, once the passenger car rear-ends the trailer, the impact will directly act on the middle and upper part of the A-pillar, causing the A-pillar to be bent and pulled. The compressive strength of general materials far exceeds the flexural tensile strength, so don't underestimate the difference in this position, the ability of the A-pillar to play the role of a high-strength material varies greatly.
As a result, without the energy absorption of the front of the car, the A-pillar is like a boxer being kicked without a headcover, and the heavy blow damage is full.
Therefore, why is it that in the rear-end truck accident of a passenger car, the seemingly unserious low-speed rear-end collision is also likely to cause a tragedy.
However, in the previous official test system, especially in the frontal crash test, there was no test scheme for the direct damage of the A-pillar - even a small offset collision with a very high degree of damage. Because the point of impact fell on the door frame, the A-pillar at least had a helper.
Are all the rear-end half-hanging tests initiated by the private sector reasonable?
The rear-end semi-trailer test initiated by the private sector has not been unified so far.
For example, in 2021, Hongqi H9 did a two-car rear-end collision test. The front car rear-ended the truck at a speed of 50km/h, and the Hongqi HS5 in the rear rear-ended the Hongqi H9 again at a speed of 50km/h.
Previously, many people suspected that this test speed was unreasonable. And now that I have seen more, I can understand the good intentions of the red flag.
Because this method is indeed relatively close to the common collision situation, although there is still a gap from the limit, it can already explain a lot of problems.
Different from the secondary rear-end collision simulated by the domestic Hongqi H9, the American IIHS (Insurance Institute for Highway Safety) is a rear-end trailer with a test car (mainly a car with a lower body) at a speed of 56.3km/h, and the proportion of rear-end collision positions is 30%, 50%, and 100% respectively.
The reason why IIHS simulates different angles is to simulate whether the car can still protect its occupants without maximizing its defensive potential.
This is a traditional performance of the IIHS, and they have always paid special attention to the damage after offset collisions, after all, the famous 25% small offset collisions were first implemented by them.
Recently, however, the media has accelerated the collision.
Increasing the collision speed to 80 km/h is clearly simulating an extreme crash situation, especially a crash on a highway.
However, I personally feel that the consistency of this new test is very lacking, and there is no comparison. Because in these crash tests, not only did not unify the model and counterweight of the semi-trailer, but the three test vehicles: Wenjie M7, Tesla and Xiaomi SU7 collided with the trailer several times, which were also very different.
Among them, the different depths of incursion mean the probability and extent of the A-pillar being hit directly.
It is not difficult to find that the depth of intrusion in these tests is getting smaller and smaller, so the probability and degree of direct impact of the A-pillar are also lighter.
This is unfair to any of the passenger car brands being tested.
In other words, the test was more like a 100% frontal collision with a passenger car than a collision with a trailer. In other words, this 100% frontal collision has long been the best project for today's automobiles, and the pass rate ranks first all year round.
The ultimate purpose of such testing
It is to assess the safety of the trailer
In fact, in car collisions, there is a more professional concept - collision compatibility. Automotive compatibility refers to a car's ability to protect its own occupants in a collision, as well as the occupants of the opposing vehicle.
The main topics of his research are on cars (trucks or pickups) with large body sizes. For example, in North America, in 2011, the safety of anti-drilling devices installed on the rear and side of trucks began to be studied. IN 2017, THE IIHS LAUNCHED THE TOUGHGUARD AWARD, WHICH IS ONLY FOR TRAILER BRANDS THAT PASS ALL THREE TESTS.
For example, the previous two generations of Pioneer trailers (2007 and 2013 models) failed the 50% overlap assessment. So, in 2015, Pioneer redesigned the trailer and finally got the approval.
By the way, the IIHS test car mentioned above has been using the 2010 Chevrolet Corvette as a test car, and this has been written into the test protocol.
Therefore, the "car collision with trailer" test done by various domestic car media and car companies is, in the final analysis, urging those commercial vehicle brands. After all, domestic car compatibility research started late, and the safety of trailers is indeed quite bad.
Although the current mandatory national standard has a test on the safety protection ability of trailers, the test speed of GB11567.2-2001 "Requirements for the Rear Underside Protection of Cars and Trailers" is only 32km/h, which is only a turtle speed in the city, and it is difficult to play a great role.
End
Is the test initiated by the people "chest broken boulder" a lively picture, or is it really representative?
Looking at it now, I think this is indeed a very new test project that is very suitable for national conditions.
On the one hand, the domestic trailer anti-intrusion device is bad, and it is indeed easy to cause serious accidents. On the other hand, the structure of passenger cars means that they will still suffer a lot of damage even if they collide with the trailer at medium and low speeds.
However, at present, more and more car companies are choosing to use hot-stamping steel plates on the A-pillar to greatly improve the structural strength of the A-pillar.
But the most important thing is not to follow the big trailers on the road unless necessary. Especially at high speeds, the behavior of wanting to break the wind with the help of a trailer is absolutely unacceptable.