What Makes a Car Safe?

Whenever road accident data is reported in the media, or in the event of a particularly ‘newsworthy’ tragedy such as the terrible thirty-car accident on the M5 recently, the question of road safety is brought up.
The automotive industry has made some spectacular technological advances over the last century, but one Ncap Rating My Car of the biggest and most important areas of development has been safety. But what makes a ‘safe’ car?
The broad umbrella of ‘safety’ is usually divided into two categories: active safety and passive safety. Active safety is the car’s ability to avoid having an accident. Passive safety is the car’s ability to protect its occupants once it is actually having an accident. For example, anti-lock brakes are an active safety feature, while airbags are a passive safety feature. In this article, the first of a three-part series, we are going to look at passive safety. In the next article we will look at active safety, and in the final instalment we will look at what you can do with the car you are already driving to make it safer.
Passive safety
Most people tend to associate ‘safety’ with ‘passive safety’ rather than avoiding the accident in the first place. This is not surprising, because most government regulations and high-profile programs like the EuroNCAP safety ratings concentrate heavily on how cars protect their occupants in an accident. Equipment like airbags and seatbelts are heavily regulated, and cars have to achieve certain levels of performance when crashed into barriers and poles at certain speeds.
The improvements made in passive safety over the last thirty years are staggering. Spend some time watching videos of crash tests on YouTube or the EuroNCAP website and you will be shocked at the violence of a full-speed car crash. And for anyone who thinks that an airbag is a big soft pillow which reaches out of the steering wheel to lovingly embrace you in an impact, you will be unpleasantly surprised to see how explosively an airbag deploys. “Explosively” is an appropriate word, too, because your airbags and seatbelts use pyrotechnics (i.e. explosions) to yank your seatbelt tight and trigger the airbags around you in milliseconds once you commence having an accident. An airbag may save your life, but it may also give you a broken nose or cheekbones in the process. A seatbelt will hold you securely in place but could snap your collarbone as it does so.
Modern seatbelts are a technological marvel compared to the original idea of a fixed-length belt which simply strapped you to the seat. A 21st century seatbelt will allow you flexibility to move around as you need to under normal driving circumstances, but in the event of an accident it will carefully yet very rapidly pull you back into the seat and let you out again if necessary to control how quickly you (and all your internal organs) slow down as the car itself breaks up around you. The seatbelt and airbags are designed to work very precisely together. Airbags deploy in specific directions, at specific speeds, and the seatbelt makes sure you are held in the right place to benefit from that. There’s no point having an airbag go off to absorb your impact if you miss it because you were thrown around the cabin instead. Airbags on American cars are designed to be much bigger and more powerful than on European cars, because fewer Americans wear seatbelts and the airbag has to try and stop an unrestrained occupant instead of a properly-belted one. Thankfully, seatbelt usage in American has improved significantly in recent years, although it still lags behind the rest of the civilised world. In fact, in New Hampshire there is still no law requiring seat belts to be worn!
Modern cars are also designed to crumple in very specific ways, to absorb and divert as much impact energy as possible away from the cabin. The cabin itself is heavily reinforced so it does not crumple, which is why car pillars have become much thicker in recent years, while at the same time window lines have become much higher. If you look at a car from the 1960s or 1970s, you will see it has lovely thin pillars and lots of glass all around, which is great for visibility but won’t stop anything trying to come through into your cabin. The chunky, almost armoured look of many modern cars might not be as pretty, and it definitely impedes visibility, but it will protect you much better if you happen to be inside during an accident. Doors are heavily reinforced with smaller windows and higher windowlines, to protect you in a side impact. Fuel tanks have to be mounted in a certain way and constructed so that they don’t rupture and spill fuel everywhere in an accident to reduce the chance of fire. Headrests are carefully designed to protect your head and neck from whiplash in a rear impact. The steering column has to collapse in a certain why so it doesn’t impale the driver in a frontal impact. The engine will break away from its mountings and slide under the car, and virtually every component on the car is designed to break in a certain way to absorb impact energy and deflect it away from the cabin.
This crumpling and energy absorption is why you still hear the old cliche that “new cars fall apart too easily” compared to older cars. That is absolutely false – older cars are far less safe in an accident precisely because they don’t crumple in a progressive and controlled manner. If that older car runs into a wall/tree/other car at 40 mph, it effectively stops instantly and all the energy is transferred to the occupants inside, so you keep moving at about 40 mph, usually into the dashboard or through the windscreen.
Crash test standards are getting ever tougher. EuroNCAP most recently overhauled its rating system in 2009, making a 5-star result in the 2009 test significantly harder to achieve than for 2008 and earlier. When looking at a car’s crash-test results, it is important to check which test protocol was used. Ratings are given for the protection of both adult and child occupants, as well as pedestrians, in the new 2009 protocols.
All of the above is merely a glimpse into the technology behind how your car behaves in a crash. In the next part of this series, we Padova Classic Car Show 2019 will look at how your car helps you avoid a crash in the first place, which is where a lot of development is currently taking place.

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