Let’s talk about Merc E-Class safety and what could go wrong

A file photo of a Mercedes E-Class. PHOTO| FILE| NATION MEDIA GROUP

What you need to know:

  • Statistically speaking, this trend is what we could call “noticeable” or “significant”.
  • There are those circumstances that we can do nothing about, for example, when stuff falls off a moving truck and goes through your windscreen.
  • This is not unheard of, but the safety engineers at Mercedes-AMG, at Volvo or even at Mobius, cannot do anything about that beyond improve auxiliary safety features such as braking and stability control systems to enable the driver to maintain control of their vehicle at all times, including during emergency stops or when swerving at high speeds.

Hi JM,

I enjoy reading your educative articles. Keep up the good work!

 I currently drive a VW Touareg but I have been contemplating buying a Mercedes E-Class that seems “less bulky” for the town-running executive that I am.

However, following the recent accident involving the E-Class of the late Nyeri governor, I’m having second throughts, I just could not come to terms with how a guardrail could  slice through a Mercedes Benz like a knife through a piece of cheese! It’s mind boggling!

Can you kindly touch on some safety features of the E-Class and what could have gone so wrong in that accident?

That will help me, and possibly someone else, make an informed decision before buying the E-Class.

Moses Kibandi

 

Hello Moses,

You are right, the accident was mind-boggling. But then again, it is what we call a “freak accident”, the kind of thing that no one really sees coming.

And when I say no one, I mean no one at Mercedes. We here might have seen its ilk before – a blue Premio suffered the same fate earlier and a Nissan Hardbody pickup later.

Statistically speaking, this trend is what we could call “noticeable” or “significant”.

There are those circumstances that we can do nothing about, for example, when stuff falls off a moving truck and goes through your windscreen.

This is not unheard of, but the safety engineers at Mercedes-AMG, at Volvo or even at Mobius, cannot do anything about that beyond improve auxiliary safety features such as braking and stability control systems to enable the driver to maintain control of their vehicle at all times, including during emergency stops or when swerving at high speeds.

They cannot make windscreens out of armoured steel for common sense reasons, and in return they expect drivers to be sensible enough to maintain a reasonable following distance from all traffic, not necessarily trucks carrying high-risk cargo.

Then there are freak accidents such as the one that claimed the governor’s life. Nobody expects a guardrail to turn coat and act as a lance, penetrating the passenger area of a much-lauded motor vehicle from one of the finest automakers on Earth.

This is the part where we dabble in a bit of physics. Have you seen speed boat competitions where it all goes belly-up, sometimes literally, for the competitors? Random pieces flotsam and jetsam — sometimes as simple as twigs and driftwood — rips the hull asunder, slicing it in two or more parts and the result is gruesome.

This is because at certain speeds, objects that are otherwise relatively harmless turn into deadly projectiles that will destroy anything they come into contact with. Speed matters.

The hardness or softness of the object is moot if the impact speed is high enough.

Think of water. Water is so soft that it is easily penetrable and has no definite form; it has to assume the shape of whatever contains it.

However, both high-speed impact with water and impact from water such as a jet or high-flow high-pressure stream become instantly destructive.

Now imagine what an abruptly truncated guardrail will do to a speeding Mercedes. It will go through the Benz like a knife through cheese, to use your own words.

One could argue that the entire vehicle could be made from sterner stuff — parts of it are, anyway— but there are two counterarguments to this.

Firstly, the reason why motor vehicle safety standards have gone up nowadays is the use of energy-absorbing designs and materials which collapse upon impact, absorbing the kinetic energy that would otherwise send a fatal shock wave through the vehicle, dooming the occupants.

However, the crumple zones are usually at the vehicles’ extremities: bow and stern, with the centre section being stiffest.

Secondly, the forward integrity of a motor vehicle safety cell in itself in inherently flawed out of necessity. You could build a safety cell out of concrete and titanium, but your own engineers and designers will tell you that the bulkhead needs apertures for it to work in the real world.

Where will the steering column go through? You need a hole for that.

Where will the pedal connections go through? You need another hole for that. Where will the HVAC system feed its thermoregulated airflow through? Yes, you are right, one more hole for that as well... Keep in mind that these vehicles are sold in both right-hand and left-hand drive markets, and these are not usually differentiated at the early stages of manufacture, so the frame is assembled or cast or pressed to cater for both.

The people fitting the ancillary stuff will take care of whatever little details like which side the driver sits  on afterwards.

The chassis, therefore, comes with provisions for both, which in turn means that the forward bulkhead is full of holes by design. Holes mean zones of weakness and potential entry points for sharp narrow objects... such as a guardrails.

 

***

WHAT HAPPENED TO A CAR THAT IS SO HIGHLY RATED?

The late governor’s car was a facelifted W212, built between 2013 and 2016, in E250 guise.

Some hasty Google-Fu reveals very high marks in the Euro-NCAP safety ranks, scoring 86 per for adult occupants, 77 per cent for child occupants and 86 per cent in safety assist, which are the three relevant parameters to this circumstance.

These high scores are from an entire raft of airbag and seat-belt load limiters and pretensioner set-ups as well as the design of the vehicle’s bones, which is what I think is of great interest to us.

I downloaded the Euro NCAP results file for the W212 and pored over it and noticed a very interesting little sentence in paragraph 2 of the comments section, titled “Adult Occupant:  “In Euro NCAP’s frontal and side barrier impacts, the PRE SAFE system was not activated...”which immediately raised my antennae, but then it goes on to say: “... the passenger compartment remained stable in the frontal impact... Dummy readings indicated good protection of the knees and femurs of both driver and passenger...”

This clearly reads that the Merc’s passenger cell passed the safety test so well that it did not need any intervention from their cauldron of electronic magic* (see Addendum) to keep occupants unscathed.

But then again the testers were crashing into walls and barriers, not sharp needle points, because in the real world, most people crash into walls and other vehicles, not the tip of a sword. Can we really blame the car? I’d rather we didn’t.

You do not want the might of the German automaker’s legal war machine crossing international waters and pitching camp at your doorstep.

To try and blame their bestselling vehicle for failure to live up to its name is to cast aspersions on their qualifications as car manufacturers, and you dare not imply that for the nameplate that invented the motor vehicle.

To go down this path, you will need reams and reams of research and investigation results, ready to defend your thesis on why you think the Germans kut korners on safety, and a solitary single-vehicle accident does not constitute “sufficient proof”... Or else you will have to eat crow and it doesn’t taste too good.

Did the car fail? No.

 

***

POINTING FINGERS

These types of accidents bring to the fore the latent issue of road safety and the inevitable blame game that follows. We have seen it with the “rollover-prone” Landcruiser Prado and now it seems Mercedes-Benz is about to be dragged into the mire.

Sure, perhaps for what it costs, the governor’s E Klasse was expected to be as impenetrable as a nuclear bunker, which goes to show how poorly the general public understands physics and the intricacies of motor vehicle assembly.

The guardrails that claimed the leader were probably of suboptimal employment, but then again looking around reveals guardrails worldwide are not always the lifesavers we take them to be.

We can ask Mercedes-AMG for answers on the hull breach their vehicle suffered and we can blame the government for half-assed road design, but at the end of the day, that accident was primarily the responsibility of someone at the scene on that fateful day.

There was mention of a wayward motorbike, and/or perhaps a truck; I don’t know and I can’t tell because I awoke to the news on social media where so many things are said.

The driver might or might not have admitted to taking liberties with the prevailing speed limits.

It was a bit greasy out there owing to some pre-dawn precipitation, and it was very cold: two known and sworn enemies of tyre grip. Something definitely went terribly wrong, and it was someone’s fault, someone who was there that morning; not the engineers at Stuttgart and not the tender-toting bureaucrats at the Ministry of Roads and Public Works.

The big question is not how safe German cars are (the answer is “very”) or what type of civil engineers the government hires (the answer is “varied”), the big question remains why the Mercedes crashed in the first place.

RIP Dr. Gakuru. Your death was as untimely as it was sad.

(*Addendum: PRE SAFE is an electronic ghost that lives in many Mercedes-Benz road cars. It can anticipate accidents and prime passive safety equipment such as restraints and protection systems in readiness for the inevitable. It requires a whole other article to explain exactly what PRE SAFE is and how it works, so we won’t get into that here...)

 

Having car trouble? Write to [email protected] for free advice.

 

***

Be warned, guardrails can turn into killers

Now, it so happens that I live near a guardrail and so I took a little walk in the name of research. The result is the photos below.

Clockwise: Figure 1 to 4 illustrate different sections of a guardrail. Guardrails have a sole purpose to their existence: to prevent motor vehicles from accessing restricted areas. PHOTO| FILE| NATION MEDIA GROUP

Guardrails have a sole purpose to their existence: to prevent motor vehicles from accessing restricted areas such as roadside obstacles, other lanes of traffic or a ravine here and an abyss there should they leave the road deliberately or otherwise.

By design the guardrails need to be strong enough to withstand the weight, speed and attendant momentum of a car driving smack dab into them, but in the same vein, their Young’s Modulus (flexural stiffness) is set such that they need to be elastic enough to both absorb and deflect the kinetic energy of the wayward vehicle without exceeding their tensile strength limits and breaking.

This doesn’t always happen. Material science is a difficult subject, I know.

In short, you are meant to hit a guardrail at an angle, and that guardrail is meant to either bring you to a stop a little more gently than a concrete wall would but still violently enough that you will not forget to drive carefully next time, or simply bounce you off and throw you back onto the same road you are trying to unwittingly exit. Again, this doesn’t always happen.

Airbags deploy, engine and gearbox will not necessarily be intact.

A photo taken exactly 700 metres from my house shows how guardrails are meant to deform when hit by a motor vehicle.

They still maintain their overall integrity (by not breaking or shearing) but they take one for the team by losing shape. Such a guardrail is due for replacement because one cannot vouch for its ability to withstand another similar impact.

It shows how different sections of a guardrail are attached to each other to form one long sector and this is where it gets interesting.

The fasteners look like giant rivets, and much as they are steel, their cross-sectional areas do not look sufficient to withstand a substantial impact, especially from a heavy vehicle.

That joint looks like it would give way when hit hard enough, and once it does, what is left is the knife edge with pointy corners indicated by the yellow arrows, after which what you have is not so much a guardrail as a giant rapier coming at you at 100 km/h. This sharp edge, I presume, is what claimed the administrator’s life.

It  shows exactly what I meant in regard to Fig 2. The fastener between the guardrail and the bollard has started to yield, whether of  its own accord or because it fielded a few smacks in its lifetime is a matter of conjecture, but it is clearly on its way out.

It won’t take a very hard knock to collapse that joint, after which the safety feature turns into a weapon.

This shows the termination of this particular sector of the guardrail. The edge has been rounded off, presumably to blunt the tip somewhat, and a reflector attached for good measure.

Within the circumference of the folded reflector, we see exactly what might have done the good doctor in, the sharp edge of the guardrail that breached his motor vehicle.

The common denominator for both vehicle and guardrail is that both are designed to deform on schedule and sacrifice themselves for their human masters.

The common denominator for both vehicle and guardrail is sometimes the fates conspire to arrange an unfortunate confluence of events, ensuring fatality despite humanity’s best efforts.

Yes, a little research shows ours is not a uniquely Kenyan problem after all: guardrails have been responsible for some very serious personal injuries outside our borders too.