THE TRUTH ABOUT CRASH TESTS: interesting article by MB

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THE TRUTH ABOUT CRASH TESTS

Mercedes-Benz has set itself the goal of building the safest cars in their class. Especially as far as passive safety is concerned, it deliberately pursues an integral concept designed to provide excellent all-around protection for vehicle occupants, but also a reasonable level of compatibility with other vehicles on the road. In this way we show responsibility for the safety of road traffic as a whole and make a real contribution towards preventing casualties.

Innovations that have caught on

A whole range of technical developments designed to improve passive safety, which are now largely taken for granted in the automotive industry, originate from Mercedes-Benz. These include:

· Body with rigid passenger compartment and defined crumple zones

· Deformable steering column (to prevent intrusion into the interior).

· Supplemental restraint system including front airbags, emergency tensioning retractors and knee bolsters.

· Integrated belt force limiter for front seat belts.

· Automatic child seat recognition for the front passenger seat.

· Automatic rollover bar (SL, CLK Cabriolet)

· Integral seat with integrated belt system (SL, CL)

Safety to international standards

Mercedes-Benz is present in virtually all markets around the world. Each model series meets all safety standards applicable worldwide.

Real accidents as a benchmark

But Mercedes-Benz doesn't just follow legal requirements; it goes a step further. Vehicle structure and restraint systems have a balanced design to provide a minimum risk of injury in the most common accident situations. A special department for accident research that Mercedes-Benz set up back in 1969 supplies the necessary basic knowledge. Up to 300 crash tests are carried out every day in Sindelfingen.

Yesterday's Mercedes standard is today's law

Mercedes-Benz has repeatedly given decisive new impetus to improving passive safety. One example is the offset crash test, first with a rigid barrier from 1979 and then with a deformable barrier from 1992. This realistic test procedure developed by Mercedes-Benz in the early 90s was used as the basis for the European crash test.

But still not always top of the class

A manufacturer that goes to so much trouble should really come out on top on every test. But the Mercedes-Benz safety philosophy is not aimed primarily at test results, but providing vehicle occupants with as much protection as possible in real-life accident situations. The result is that Mercedes-Benz vehicles do not always finish first in individual tests - especially those that have no real world merit.

We'll try to explain the different crash tests and how Mercedes-Benz safety research rates these tests with regard to their relevance to real-life accidents.
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NOT ALL CRASH TESTS ARE THE SAME

A crash test in controlled conditions helps to determine how a vehicle will behave in a collision. We distinguish between three types of crash tests:

· Mercedes-Benz safety research tests

· Legally required crash tests which every vehicle has to pass.

· So-called "rating tests", performed by independent institutes, associations or magazines according to their own criteria.

The following criteria are also checked: How well does the body convert impact energy into deformation? What acceleration forces act on occupants? To what extent are intrusions of vehicle components into the passenger compartment prevented?

Legally required tests which every vehicle has to pass

Two crash tests above all are specified in order to verify a vehicle's occupant protection: frontal and side crashes. Criteria for these tests specified in either Europe or the US apply practically all over the world. One important feature of all legally required crash tests are the acceleration forces acting on the occupants which are not allowed to exceed a specified limit.

Ratings with wide-ranging results

A number of institutions have developed test procedures which in certain cases are more demanding or different from the compulsory tests. These are known as rating tests. In order to make it easier to compare the occupant protection of vehicles tested, results are evaluated according to a simple points system. Consumers can then choose between vehicles based upon point ratings.

The result depends on the method.

Some of the rating tests are based on the institutes' own test procedures and evaluation criteria. In some cases, results are even interpreted and weighted differently.

This means that results are not fully comparable and not all rating test procedures and evaluations are scientifically founded. Their results are therefore only meaningful up to a certain point.

Incomplete simulation

No single crash test provides a comprehensive appraisal of a vehicle's passive safety. It simulates a very specific accident situation which only represents a small fraction of the large number of possible accident situations.

Safety in touch with reality

The aim of vehicle development at Mercedes-Benz therefore is not to design cars according to individual test criteria, but to produce an all-around safety concept which offers maximum occupant protection in as many conceivable types of accidents as possible, at the same time providing compatibility with other road users. Every Mercedes-Benz car is therefore subjected to a test procedure which simulates a wide range of actual accident situations as realistically as possible.
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BASIC PRINCIPLES FOR DESIGNING VEHICLE STRUCTURE

"Hard" vehicle structure

If the vehicle structure is extremely hard, the occupant cell is largely preserved, but the occupants can be exposed to extremely high loads. Before Mercedes-Benz developed the safety body with clearly defined crumple zones in 1951, all cars were designed the same way. In short, they were as rigid as tanks and therefore lethal in heavy collisions.

"Soft" vehicle structure

In principle a soft vehicle structure reduces the occupant stress load. This, however, depends on the occupant cell not being used as part of the crumple zone. Vehicles which, by virtue of their soft structure, allow deformation as far as the occupant cell when crashing into a barrier with full overlap may achieve outstanding low occupant stress loads in this kind of crash but do not provide the necessary safety reserves in offset crashes which are more common in reality.

Mercedes-Benz philosophy of structural design

The real art is to develop structural concepts which withstand the wide range of loads experienced in real accident situations. In other words, they should only permit deformation if it does not cause damage to the occupant cell. At the same time, occupant stress loads must remain bearable even in heavy collisions. According to the Mercedes-Benz philosophy, consideration of as wide a range of accident types as possible takes priority over top marks in any individual type of test.

Some Examples of different vehicle structures in a frontal crash with 100% and 40% overlap with the obstacle:

Hard Vehicle Structure:

Full Frontal Crash

Deformation: Low

Acceleration: High

Occupant stress load: Extreme

40% Overlap

Deformation: Low

Acceleration: High

Occupant stress load: Extreme

Soft Vehicle Structure:

Full Frontal Crash

Deformation: High

Acceleration: Low

Occupant stress load: Low

40% Overlap

Deformation: Extreme

Acceleration: Low

Occupant Stress Load: Extreme

Mercedes-Benz Structural Concept:

Full Frontal Crash

Deformation: Average

Acceleration: Average

Occupant stress load: Acceptable

40% Overlap

Deformation: Average

Acceleration: Average

Occupant stress load: Acceptable.

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THE AMERICAN WAY

American regulations have always had a clear emphasis: the load experienced by the occupants in a collision is a primary concern.

The Classic full frontal crash:

The important US TEST "Standard 208" against a rigid barrier measures whether the forces experienced by the dummies in the head, chest, and thigh regions are within the specified limits.

A touch of reality

In addition to the simple frontal crash, US legislation stipulates a version in which the vehicle is crashed against a rigid barrier positioned at a 30° angle.

A realistic side crash

The side crash specified in the US uses a deformable barrier. The test measures whether the load experienced by occupants in the chest and pelvic regions is within the legal limit. A special SID (Side Impact Dummy) is used to measure loads.

Special emphasis on the tank

The US is particularly concerned about the integrity of the fuel tank system. This is checked in an additional rear-end crash test and a side impact at an angle of 90°. A particularly heavy rigid barrier weighing 3,999 lbs is used in each case.

Tests:

Full frontal crash against a rigid barrier.

· Impact speed 30 mph

· Vehicle with two occupants and measuring sensors

Assessment criteria:

· Occupant stress load

· Leakage from fuel system

· Vehicle structure

What Mercedes thinks:

A test introduced back in 1965 which, due to modern restraint systems, is not especially demanding by today's standards. It is used in the US to test passive restraint systems (i.e. without manual seat belt.)

Frontal crash at a rigid barrier at an angle of 30°

· Speed 30 mph

· Vehicle with two occupants and measuring sensors

Assessment criteria:

· Occupant stress load

· Leakage from fuel system

· Vehicle structure.

What Mercedes thinks:

This test is a first attempt to achieve realistic deformation behavior. However, the disadvantage of this test procedure is that the car body glances off the barrier. This means that the test does not fully replicate the situation in a real accident. Once again, no great demands are made of the vehicle structure.

Side impact with a moving deformable barrier at an angle of 27° to the longitudinal axis of the barrier.

· Impact speed of 33.5 mph

· Weight of barrier 3,013 lb.

· Vehicle with two occupants and measuring sensors

Assessment criteria:

· Occupant stress load

· Leakage from fuel system

· Rescue behavior (opening the door)

What Mercedes thinks:

This test was introduced in 1993. The use of a sideways moving barrier is supposed to simulate the collision between two moving vehicles. Compared with the Euro side impact, a different side impact dummy (US SID) is used, which, for example, requires different measures from the Euro SID.

Side impact with a rigid barrier against a stationary vehicle.

· Impact speed 19.8 mph

· Weight of barrier 3,999 lbs.

· Vehicle with two occupants and measuring sensors

Assessment criteria

· Leakage from the fuel system

· Vehicle structure

What Mercedes thinks:

This side test for checking whether the fuel tank leaks has no relevance to real accident situations.

Rear-end crash with a rigid barrier against the stationary vehicle.

· Impact speed 30 mph

· Weight of barrier 3,999 lbs.

· Vehicle with two occupants and measuring sensors.

Assessment criteria

· Leakage from the fuel system

· Vehicle structure

What Mercedes thinks:

The use of a rigid barrier with a large impact area means that this crash test is also unrealistic and does not allow any accurate conclusions to be drawn as to the vehicle's actual behavior in a rear impact.

US NCAP:

(New Car Assessment Program)-developed by the US National Highway Traffic Safety Administration back in 1978. It is based on just a few relatively simple assessment criteria. The aim of this program is to compare the occupant protection of new vehicles and to make this information accessible to the consumer.

It is largely based on the legally required procedures in the US. The vehicles are, however, crashed at much higher speeds than in Euro tests. This is quite simply a test of extremes and is suited above all to evaluating restraint systems.

· Full frontal crash against a rigid barrier.

· Impact speed 34.7 mph.

· Two dummies with measuring sensors.

Assessment Criteria:

· Occupant stress load evaluated separately for driver and front passenger

· Evaluation system with 1-5 stars.

What Mercedes thinks

This first rating test which was introduced back in 1978 is a tough restraint system test which does not really ask much of the vehicle structure. The risk of injury is evaluated based on just two measuring criteria, head and chest acceleration, which, in our opinion, does not allow any conclusions to be drawn about the overall risk of injury. In the past, a number of vehicles designed in accordance with this test (soft structure) were noted for their poor offset results.

USSINCAP

· Side impact with a moving deformable barrier at an angle of 27° to the longitudinal axis of the barrier.

· Impact speed 37.9 mph

· Weight of barrier 3,013 lbs.

· Two dummies with measuring sensors

Assessment Criteria

· Separate evaluation for driver and rear passenger

· Evaluation system with 1-5 stars.

What Mercedes thinks:

Like the frontal crash, this legally required test is carried out at a higher impact speed. Only chest acceleration is measured. A good rating can be achieved with the help of measures specifically for this body region.

IIHS (Insurance Institute for Highway Safety) The IIHS has been performing its own frontal offset crash since 1995. The test procedure is exactly the same as for the Euro NCAP test, but very different assessment criteria are applied.

· Frontal crash with 40% overlap against a deformable barrier.

· Impact speed 39.7 mph

· One dummy with measuring sensors

· Bumper test at 5 mph

· Head restraint measurement

Assessment criteria

· Individual and overall evaluation of occupant stress load, occupant kinematics, vehicle structure, bumper, and head restraints

· 4 evaluation grades (good, acceptable, below average, poor) similar to 1-4 stars

· The best in the comparison test receive a special recommendation (best pick)

What Mercedes thinks:

The actual offset crash is much the same as the Euro NCAP test. As well as the frontal crash, a total of 4 bumper tests are carried out at 5 mph, and the head restraints are evaluated. Taking account of the score for different interpretations of dummy measurement, the frontal impact evaluation is realistic.

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FOCUS ON REALITY

It is not that difficult to design a vehicle to ensure that it passes certain crash tests with flying colors. Although this would produce excellent results in crash tests, it wouldn't mean a high level of safety in actuality. This is one reason why Mercedes-Benz is not primarily interested in individual crash test results, but is continually working to design the passive safety of its vehicles in line with real-life accident situations. The statistical evaluation of real-life accidents by our internal accident research department provides the basis for our internal crash tests.

Theory and Practice

At best, any given test can only simulate a specific accident situation in certain conditions. Yet the effect of kinetic energy on vehicle deformation and occupant stress load depends on a whole series of different factors. A collision between a heavy sedan and a compact car, for example, is a completely different story from a crash involving two vehicles weighing the same.

Faster is not always better

A good test result achieved at high speed might make the client feel safer, but a vehicle that has been designed specifically to pass these test conditions is bound to have a particularly rigid front end. In other words, safety for one vehicle is bought at the expense of a higher risk of injury for other road users.

Resolving conflicting aims

Modern vehicles have to be compact on the outside, but offer plenty of space inside. They should cushion peak acceleration gently in a collision (energy-absorbing front end), but prevent intrusions into their interior (rigid occupant cell). They should be lightweight, but resist loads in a side impact. Such conflicting aims call for a balanced concept that provides maximum occupant protection in as many different situations as possible.

All-around protection with a sense of realism

The development goal at Mercedes-Benz is balanced all-around protection for maximum possible safety in all accident situations put together. We also place special emphasis on protection for other road users, thus demonstrating the considerable responsibility we feel for general road safety. The result of this safety philosophy is that in comparison tests under laboratory conditions that stimulate a very specific accident situation, Mercedes-Benz vehicles do not always come away with top marks. But they are able to offer their occupants a high level of all-around passive safety in the real world of road traffic.

Far more than required

Before the client takes delivery of the first Mercedes-Benz in a new series, dozens of vehicles will have already been through situations that he or she will hopefully never experience. These include not only all the legally required test procedures and rating tests, but also numerous practical tests that verify the safety of a Mercedes-Benz in real-life accident situations.

Compatibility cannot be simulated

The barrier impact test is not an adequate means of simulating what happens when two vehicles of different sizes and weights crash into each other. Every Mercedes-Benz model series is therefore subjected to a compatibility test involving another vehicle. This is an established part of the Mercedes-Benz safety philosophy.

Head-on into a tree

Point-shaped obstacles such as trees or lamp posts are not included in any legally required test procedure. Mercedes-Benz therefore performs special side and front crashes to examine its vehicles' structural safety in these extremely tough, but by no means unusual conditions.

A matter of design

Protection for pedestrians and cyclists depends first and foremost on a vehicle's external contour. Mercedes-Benz therefore checks whether its vehicles meet the necessary requirements for reducing the injury risk as far as possible.

TESTS FROM THE MERCEDES-BENZ TEST PROGRAM:

Vehicle/Vehicle crash

· Frontal crash with approx. 50% overlap.

Assessment criteria

· Compatibility

· Structural rigidity

· Real deformation behavior

· Occupant stress load

· Leakage from fuel system

What Mercedes Thinks:

This type of test produces the most realistic results of all. Mercedes-Benz developed the offset impact with a deformable barrier based on the results of this test and findings from real-life accident situations.

Center-post impact

· Frontal crash against a solid post

Assessment Criteria:

· Structural rigidity

· Restraint system

· Leakage from fuel system.

What Mercedes thinks:

This type of accident is relatively common in real life. The point-shaped load is particularly difficult for the vehicle structure to withstand.

Rear Impact

· Rear-end collision with a deformable barrier.

Assessment criteria:

· Structural rigidity

· Intrusions into the interior

· Leakage from fuel system

· Occupant stress load

What Mercedes thinks:

Realistic simulation of the common rear-end collision with the aid of a deformable barrier.

Vehicle Rollover

Assessment Criteria:

· Rigidity of occupant cell

· Occupant rescue.

What Mercedes thinks:

It is a practical test of structural rigidity and is supplemented by a roof drop test to check roof structure strength.

External Safety

· Collision with pedestrians and cyclists

Assessment Criteria:

Risk of injury for pedestrians and cyclists/motorcyclists.

What Mercedes thinks:

These realistic tests check measures designed to help reduce injury severity to pedestrians.
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PROOF

I was planning on writing a piece explaining what all of that testing philosophy meant to you and me, people who trust their lives to Mercedes-Benz every day, but this article did it better (Condensed).

Posted Fri., Nov 14, 2003

2 dead, 4 injured in Los Altos crash

By Chuck Carroll, Mercury News

Two women were killed and four people were injured in a two-SUV rollover crash on Highway 280 in Los Altos Thursday night.

All the victims are from San Jose.

A 19-year-old female driving an Isuzu Rodeo with four passengers apparently lost control of her vehicle as she traveled south on 280 just south of El Monte Road before 7 p.m. The Rodeo struck the Mercedes sport utility vehicle driven by a 27-year-old woman, causing both SUVs to tumble like a pair of dice.

A 16-year-old female passenger in the Isuzu, who was not wearing a seat belt, died at the scene after being ejected from the vehicle. The 19-year-old driver, who was buckled up, also died. The other passengers, a 32-year-old female, a 34-year-old male and an 18-year-old male were treated for minor injuries.

The driver of the Mercedes did not seek hospital treatment. (Emphasis added, CRR)

[CPSDarren]

Is this article reprinted from another source (website, brochure, paper, etc)? If it is and that source is copyrighted, do you have permission to reprint it here?

[wondering1]

Still no source but check this out: http://www.curtrich.com/december2003.html

[southpawboston]

the article about mercedes is compelling, but it's also PR. is it mentioned anywhere in that article that volvo has also had many safety "firsts"? like the 3-pt seatbelt? also, i think it may have been volvo who was first with the crumple zones. and ABS brakes were developed by the french, and first implemented in a motor vehicle by chrysler, of all makes... way back in the 70s! MB is not the only company with this philosophy towards safety.

[tl01]

Originally Posted by southpawboston

the article about mercedes is compelling, but it's also PR. is it mentioned anywhere in that article that volvo has also had many safety "firsts"? like the 3-pt seatbelt? also, i think it may have been volvo who was first with the crumple zones. and ABS brakes were developed by the french, and first implemented in a motor vehicle by chrysler, of all makes... way back in the 70s! MB is not the only company with this philosophy towards safety.

I thought Mercedes pioneered the crumble zone...

http://www.answers.com/topic/mercedes-benz
The "Safety cage" or "Safety cell" construction with front and rear crumple zones was first developed by Mercedes-Benz in 1951.[16].

[aisraeltax]

Originally Posted by CPSDarren

Is this article reprinted from another source (website, brochure, paper, etc)? If it is and that source is copyrighted, do you have permission to reprint it here?

i dont have a link....i found it on another message board. i thought it was ok to post info. on crash reports here.

[southpawboston]

Originally Posted by tl01

I thought Mercedes pioneered the crumble zone...

http://www.answers.com/topic/mercedes-benz
The "Safety cage" or "Safety cell" construction with front and rear crumple zones was first developed by Mercedes-Benz in 1951.[16].

ah, so you are right. they did implement that concept first...

[UlrikeDG]

The person who wrote something "owns" it, and you shouldn't copy it without their permission. It is OK to post a short excerpt and include a link to the original, however.

[TechnoGranola]

The article doesn't have any references, so I am unsure of where the info is actually coming from? I mean, did some random person write it? Is the info directly from MB? Is it from some other 3rd party? It may be 100% valid, but there aren't references provided so that a person can take a look and see if this is just PR or something else. I am very interested in vehicle safety and some of this article interests me, but right now, I can't tell if it's a sales pitch or a legit, referenced article.

As for the "proof" story...the Isuzu Rodeo isn't exactly a top-rated vehicle in crash tests and also doesn't get a great rollover rating, so I'm not sure what this story is proving? It also doesn't state what model of MB SUV was involved in the crash so it's not even possible to see if there is any crash data existing for the MB. This story is anecdotal at best and doesn't provide enough details of the accident for us to know if the reason the MB driver survived was due to her being in a safe vehicle or due to the dynamics of the crash.

ETA: and I am meaning that the actual article doesn't have references, not that the OP didn't post a reference (although that would be helpful too!)

[southpawboston]

Originally Posted by technogranola

As for the "proof" story...the Isuzu Rodeo isn't exactly a top-rated vehicle in crash tests and also doesn't get a great rollover rating, so I'm not sure what this story is proving? It also doesn't state what model of MB SUV was involved in the crash so it's not even possible to see if there is any crash data existing for the MB. This story is anecdotal at best and doesn't provide enough details of the accident for us to know if the reason the MB driver survived was due to her being in a safe vehicle or due to the dynamics of the crash.

right. we have no way of knowing how each SUV really performed from that story... it's an uncontrolled crash test. for all we know, the rodeo could have flipped 10 times, and the MB twice...