Your piece on car safety last week reminded me of the Mercedes that recently burst into flames upon hitting a wall. I thought Mercs were among the safest cars in the world and would have mechanisms to prevent such a result. Or do I rate them too highly? What happened in that case?
All cars are highly flammable with abundant ingredients to start and sustain an inferno. They run on explosive fuel. They generate sparks. Parts of their engine reach temperatures of hundreds of degrees, and the exhaust manifold, brakes and turbo can get even hotter, “red” hot, even “white” hot.
These days they have plenty of plastic components, fabrics, and reactive metal alloys. They have wiring systems that can cause electrical shorts, and batteries that contain acid (potentially explosive) and can deliver high amperage downloads – enough to weld steel, never mind ignite volatile fuel. Their low-voltage is amplified from 12V to >15,000V by coil(s) with the very purpose of generating sparks.
It is a testament to intrinsic standards of design, starting with fuses, that fires don’t happen more often, and almost never when a car is simply motoring along the road. Even in severe accidents, fire is very rare: I would guess that the chances are less than 1 percent.
Nevertheless, we are rightly required to carry a fire extinguisher in our car and should know where it is in a quick-grab place in case of emergency for ourselves or any other road user. Rally cars, for which a heavy crash and fire moves up from remote possibility to high probability, among many extra safety precautions, are all fitted with built-in extinguishers that inundate the whole passenger compartment with retardant powder at the bash of a button next to the handbrake.
Over more than a century of motoring history, there have been some cases of fire-related design defects in specific makes and models, but not, to the best of my knowledge, in recent decades. The freak set of circumstances that lead to an accident fire can happen to any car.
I do not know which accident you refer to, but if it was the one in the Pangani tunnel or the one on the Thika Highway, then the fact that the car was a Mercedes is almost certainly coincidence. All Mercs now have an NCAP safety rating of a high 4 or the topmost 5. Their general design and engineering standards are not the best in the world, but they are renowned and on the leader board. The NCAP front-end crash tests drive vehicles into deformable concrete at 60kph. At that speed, Merc passenger cells remain intact. The picture in the Pangani tunnel shows a front roof pillar almost ripped off its mounting, completely away from the door, and distorted enough to fold the middle of the roof. The front-end crumple zone contents are completely pulverised. The issue here is not the car’s make, but that it was probably travelling at considerably higher speed than 60 when it hit concrete. This impact was truly massive, and there are any number of ways this car’s (or any car’s) inflammable ingredients could have met in the wrong place.
In another incident, the cause of a Merc catching fire while motoring on the Thika highway was not diagnosed by newspaper reports, but the driver’s report of engine jerks would be rational line of enquiry, perhaps intermittent fuel starvation caused by a big fuel leak which generated vapour at just the right mixture with air to be ignited by heat or an HT wiring fault. As the vehicle was completely destroyed by flames, forensic investigation would be limited.
