On the road with accident researchers from Mercedes-Benz

It was the first cold winter morning in quite some time. In fact, it was so cold that Stefan Sellner first had to scrape a thin film of ice off the windshield of the white E-Class Coupe before work could get started. Work was the operative word here, since it was obvious that the vehicle itself wasn’t going anywhere. Indeed, it was pretty clear that the car in the parking lot of a Mercedes-Benz dealership wouldn’t be leaving its location any time soon, despite the fact that it was only a few months old. The vehicle’s radiator grille was completely dented, the bumper was on the ground next to the car, and the deep scratches on the side of the body looked like a thick scar on what was otherwise a flawless diamond-white paint job.

However, it was precisely these dents, scratches and dislodged components that had led Stefan Sellner and his colleague Uwe Nagel to this location. Both of them work at Mercedes-Benz Accident Research in Sindelfingen, Germany. And for them the white coupe was just part of a normal day on the job. Nagel had talked on the phone with the driver of the car involved in the accident a few days previously, and he remembered quite well what the driver had told him about the crash. “He was driving on the motorway in the rain, in the left lane,” Nagel explained. “He says the car then suddenly went out of control. He tried to regain control of the vehicle by steering and braking. This caused him to spin around, after which he crashed into the guardrail head-on and ended up stopping on the shoulder.”

What the accident researchers could see in front of them fit in well with the driver’s description. “Based on the damage we see, we can understand pretty well what the driver described,” said Nagel. Still, it’s not unusual for the experts to discover other details when making an initial examination. In this case, for example, they determined that another severe impact must have occurred between the rear of the vehicle and the guardrail — presumably right before the car came to a stop. The driver had not mentioned this during the phone call. Nagel had encountered this type of thing many times before. “Drivers often can’t remember all of the details after an accident,” he explained. “Everything happens so quickly; for a second the whole world is turning around and your natural coordinate system can no longer determine what’s in front of you and what’s behind. It’s only after the vehicle stops that you regain your bearings.”

Translating an accident into data, facts, and figures

Fortunately, the driver and his passenger were able to exit the vehicle uninjured, to get to safety behind the guardrail, and to call the emergency services. They had no bruises, cuts, or abrasions and came away without a concussion. They were very lucky that no other vehicle was involved in the crash, given the fact that their car had spun across all the lanes of the autobahn. Fate appears to have been on their side that day, even though their white E-Class Coupe was totaled — which of course is what had brought Uwe Nagel and Stefan Sellner to the dealership parking lot.

Accident researchers at Mercedes-Benz go into action whenever a Mercedes-Benz car or a smart has an accident within a 200-kilometer radius of their offices in Sindelfingen. Obviously, they don’t head out for every little dent. Instead, they focus on accidents in which people are injured or a vehicle is deformed to a large extent — but only if the car in question is a current model. This makes sense, since as long as a model series is still on the market, the knowledge the accident specialists gain can often be incorporated into the further development of the vehicle on short notice.

“Our goal is to interpret the traces on the vehicle in order to be able to understand what happened,” Nagel explained as he walked along the side of the E-Class. Over the next few hours, he and Sellner took pictures of the damage, measured dents and scratches, and categorized everything. All of this was done in a clear and objective manner so that when they were finished, only data, facts, and figures would remain from the accident.

Experience is the key to interpreting the damage

So how exactly do the accident researchers go about their work? “The first step is really always to get a feel for the vehicle in its current state,” says Nagel. “You walk around the car once, take a look inside, and take some time to gain an overall impression and look for exceptionalities. It’s only after you’ve done this that you can start looking at the details.” The researchers generally conduct their examinations in pairs, with one expert documenting the damage to the car in photographs and the other doing the same in writing. The photos always include several standard shots that are taken in order to ensure that different accidents can be compared. After that, they start taking pictures of the details — e.g. scratches in the paint, damaged components, and abrasion marks on the seat belt. Written documentation is done using a tablet equipped with special software. This works like checklist which asks for information about each individual component. There’s a numeric code for every conceivable type of damage. All the information the accident researchers collect when they inspect the vehicle is stored in a large database.

You need to have a lot of experience to be able to correctly interpret accident damage and use it to reconstruct exactly what occurred in the decisive seconds of the accident. Stefan Sellner is 49 years old and has been working at Accident Research since 1998. “When I was a kid, I liked to crush soda cans because I was fascinated by the way they deformed,” says Sellner. “When I was a teenager, I became interested in the way vehicles get damaged. Then, while I was studying mechanical engineering, I had the opportunity to participate in an accident-reconstruction project for one semester.” Uwe Nagel, 55, has been at Accident Research since 1991. “I’ve also always somehow been fascinated by accidents,” he explains. Hermann Appel, a recognized expert for traffic safety, was Nagel’s mentor when he studied automotive technology at Berlin University. Both Nagel and Sellner are engineers, and both ended up at Mercedes-Benz Accident Research more or less right after they got out of college.

Back at the dealership, Nagel pointed to a dent in the paint. “You can learn a lot by looking at things like this on a damaged vehicle,” he said. “You just have to look closely. These abrasions here, for example, show that the force that acted upon the vehicle in the accident came from the right. This information makes it possible for us to understand the way the car was turning when it hit the guardrail. It also enables us to determine the forces the vehicle occupants were exposed to in the crash.”

And what about the effects of the crash? Sellner could rely on his experience here. “Naturally, the damage looks bad at first glance,” he said. “But if you look closely, you quickly realize that this accident wasn’t all that severe in terms of the way we look at things. One indication of that, for example, is the fact that there’s hardly any deformation of the side member. The passenger compartment is intact and the airbags deployed as they were supposed to.”

The actual scene of the accident is also closely examined

The standard procedure for accident analyses generally also involves a thorough inspection of the accident site, including the taking of certain measurements. For reasons of safety, however, such inspections can’t be carried out on the autobahn. “If an accident occurs on a secondary or a rural road, for example, we also document the final positions of the vehicles involved, the paths they traveled before coming to a stop, and the location where they hit each other,” Nagel explains. “We can then use the photos and the data from the accident site to reconstruct the accident on a computer.”

The work of the accident experts from Daimler doesn’t begin until after the police and emergency services have done their job — the Daimler experts normally don’t appear on the scene immediately after an accident. However, this begs the question as to whether such an examination immediately after an accident might yield important information about what happened. “In very rare cases, the police call us and tell us that there’s been an accident a few kilometers away from our office and that we can go to the site and have a look if we want,” says Sellner. “That could end up being interesting for us, but it’s not something that’s really necessary. Besides that, we wouldn’t have enough time to do what we need to do for our analyses in such a situation.” Indeed, the inspection of the accident site alone normally takes around an hour to an hour and a half, and a thorough examination of the vehicle involved takes two to four hours, “depending on the severity of the accident.”

Working with the data is just as important as the physical inspections on site

So how is all the knowledge and information the researchers gain incorporated into the work of vehicle developers? Heiko Bürkle laughs: “You could say that the real work doesn’t begin until the details of the accident have been entered into the database.” Bürkle, 54, is a vehicle engineer and Head of Mercedes-Benz Accident Research. It’s important to him that the work of his team involves way more than just the detective work related to the vehicle. That’s why along with three engineers who conduct the onsite inspections, his team also consists of two employees whose job is to draw the correct conclusions from the large amount of data and figures that are made available to them. Here the accident researchers from Mercedes-Benz use not only the extensive database created from the onsite analyses but also data taken from the GIDAS project. GIDAS stands for German In-Depth Accident Study and is a joint project between the German Federal Highway Research Institute (BASt) and the Research Association for Automotive Technology.

One reason why the in-house data available to the Daimler researchers is so extensive has to do with the fact that Daimler was one of the first automakers to understand that real accidents need to serve as the foundation for all efforts to increase traffic safety. Accident research at Daimler began in the spring of 1969 — one year before the German parliament laid the groundwork for systematic accident research at BASt. Heiko Bürkle’s team focuses on accidents involving Mercedes-Benz passenger cars and smart models. Since 1972, Daimler has also been operating a Truck Accident Research unit that studies accidents involving Mercedes-Benz trucks throughout Germany. In the summer of 2015, Mercedes-Benz Vans also launched a research unit to study accidents involving vans.

The legal basis of the work conducted by the accident experts in Sindelfingen is a decree issued by the Interior Ministry of the state of Baden-Württemberg. This decree stipulates that police departments may notify Daimler of any accident that occurs which involves a Mercedes-Benz vehicle. However, an extensive analysis of such an accident may not be conducted unless the car’s owner or driver consents to such an examination.

Technology is changing the nature of accidents

One might be tempted to question whether there’s really anything new left for Daimler accident researchers to learn after five decades. Haven’t they already seen it all? And isn’t the fact that road safety has, statistically speaking, become much better since the 1970s enough of an achievement? Bürkle has heard such questions before, and his response is clear: “We’re needed because we constantly face new requirements. For one thing, components, systems and technologies are continually changing. Secondly, the knowledge we gain from accident research flows into our development activities, and this leads to changes in the nature of accidents. In Germany, for example, accidents in parallel traffic, which mainly involve rear-end collisions, are on the decline. Obviously, this mainly has to do with the fact that a lot more vehicles these days are equipped with emergency braking assistance and active distance assistance systems.”

Bürkle and his team maintain close contact with vehicle development engineers. “When we notice something critical at an accident site — for example a component that is damaged in a way it shouldn’t be — we immediately report it to the appropriate specialist unit,” Bürkle explains. “This only happens very rarely, which is the way it should be.” Aside from such exceptional situations, there are two other ways in which accident researchers and developers work together: “Of course, we sometimes notice accumulations in the statistics that lead us to get in touch with development departments,” says Bürkle. “But actually, the opposite is also often the case, by which I mean that the development departments come to us with an idea that we then evaluate by determining whether or not the type of accident it addresses is actually relevant. We examine aspects such as the likelihood that the idea in question could help us prevent injuries or even fatalities.”

A range of systems inspired by accident research

The accident researchers also conduct a type of reality check for potential new technologies. One example here is the exit warning feature recently added to the Active Blind Spot Assist system in Mercedes-Benz vehicles. This feature can warn drivers when they open the door if a pedestrian or bicycle is in the blind spot, which helps prevent collisions with cyclists in particular. Before such technologies are developed in all their detail, however, accident researchers determine the statistical relevance of their functions. In the case of the exit warning feature, they found that cyclists were involved in 84 percent of the accidents of the type the feature was designed to prevent. Many of these cyclists were seriously injured, or even died, usually as a result of being thrown to the ground. It was therefore clear that the technology in question addressed a realistic accident scenario and could help save lives. The accident researchers therefore recommended that the technology should be developed. Bürkle and his team want to use their expertise to help safety technology developers focus on the important things. “Preventing accidents in general is a noble objective,” says Bürkle. “But it’s more important to prevent people from being seriously injured or dying in those accidents that do occur.”

The list of active and passive safety systems that have been inspired more or less directly by actual accidents and the work of the accident researchers is certainly impressive. The knowledge gained in the 1970s in particular helped to substantially improve impact protection in the vehicle interior and the resilience of the body structure. Later on, the PRE-SAFE® active safety system was created on the initiative of the accident researchers after they realized that most accidents were preceded by critical situations such as skidding or sudden evasive maneuvers. PRE-SAFE® exploits exactly this type of knowledge: If the system determines that an accident could be about to happen, it prepares the occupants and the vehicle for the imminent collision by, for example, triggering reversible belt tensioning as a precautionary measure.

The stability of the occupant cell protects vehicle occupants

All of the knowledge gained has contributed to a situation today in which traffic accidents often do not lead to severe injury or death, just as no one was injured in the guardrail crash involving the white E-Class Coupe. “We’re lucky that most accidents today result in only minor injuries,” says Sellner. “The number of cases of broken bones has declined significantly, for example.” When asked if it would be legitimate to estimate how the accident with the E-Class would have turned out if the vehicle involved had been a 30-year-old car rather than a brand new Mercedes, Sellner stops to consider the question for a moment. Than he gives a careful and considered answer: “The stability of the passenger compartment protected the vehicle occupants from the front wheel that was slammed back in this case,” he says. “To put it simply, you could say that if the vehicle had been 30 years old, the force of the impact could have pushed the wheel into the footwell. That could have caused a serious foot or leg injury to the front passenger. In the case of this E-Class, you can look at the interior and think to yourself that it actually still looks new.”

Figures from the German Federal Statistical Office confirm Sellner’s point of view: In 1970, when traffic fatalities had become a pressing issue in Germany, a total of 21,332 people died on German roads – and this was only in West Germany, where the total number of vehicles registered was just 15.1 million. In 2018 there were a total of 56.5 million vehicles in eastern and western Germany — but “only” 3,275 traffic fatalities. Naturally, every death is one too many. Nevertheless, the danger of dying in a passenger car due to an accident is now lower than at any time since the dawn of the age of mass car ownership.

The focus of the accident researchers has therefore long since shifted to countries in which more people lose their lives in road traffic. For example, they support SAFE ROADS campaigns  in countries like India, in which the nature of road traffic differs from Western Europe in almost every respect. “It’s important here especially to study how real accidents actually happen in such places. Internationalization therefore plays a key strategic role for us, and we work very closely and effectively with development colleagues in India and China,” says Jochen Feese who heads the department to which Accident Research also belongs.

For the accident researchers, fault is never the issue

The accident experts in Sindelfingen also now work more proactively than in the past, for example by serving as consultants who help to design safe electric vehicles. “That’s our job — to derive new safety requirements from the data we collect on actual accidents,” Bürkle explains. “We address questions such as: At which locations in the vehicle should we avoid installing high-voltage components because these areas are often damaged in accidents? Or: How can a vehicle recognize that it’s currently involved in an accident that requires the high-voltage or 48-volt systems to be shut down?”

The knowledge the accident researchers have gained to date is in any event promising. For example, the relevant electrical systems shut down perfectly in all the electric and hybrid vehicles from Mercedes-Benz that have been involved in an accident and were subsequently examined. Naturally, it’s also the case that the experts’ wealth of knowledge increases as more and more electric vehicles are put on the road — and accident research relies on exactly this experience. “The personnel fluctuation in our team is quite low, which shows that our job is extremely multifaceted — no day is like any other,” says Bürkle, who has led the team since 2001. Prior to that, he worked as an accident researcher at a vehicle inspection company, where he sometimes served as a court expert as well.

There is, however, one important difference between working as a traffic accident expert for the criminal justice system and analyzing accidents for Mercedes-Benz. This difference is important to Stefan Sellner as well. Before taking a closer look at the dented white E-Class Coupe, he said a few words that stick in the memory: “We’re never interested in the question of who’s fault the accident was. We don’t want to know if someone failed to yield, for example, or was driving too fast. What we want to find out is what we still have to do to ensure that nobody else suffers serious injury when they’re involved in an accident. That’s all we’re interested in.”