How the five most common safety features work

Safety is a parameter that has never been given much importance to while buying a car, till now though. With consumers now being more aware of global safety norms & Euro NCAP ratings, they are demanding safer cars. Seeing this, most manufacturers have updated their model line up to offer safety features even on lower end variants of their cars. Having a safety features is one thing, knowing how they work is another thing. We tell you how the most common safety features work.

Safety is categorised into 2 sub headings, Active safety & Passive safety. Active safety relates to everything that prevents you from crashing. Passive safety is everything that will protect you once you have crashed. Now we shall explain how these features work.

Seatbelts

seatbelt

This is the most basic safety feature present in every car. Most cars come with 3-point seatbelts at the front and the back(except the middle seat at the back on some cars). A 3 point belt secures your upper as well as lower body (comes around your shoulder as well as waist). In the event of a crash or heavy braking, a seatbelt is designed to restrict your forward motion thus preventing you from hitting the windscreen & dashboard. In case of a roll over, it also ensures that you stay in your seat & don’t get ejected from your car. So how exactly does it work?

The seatbelt has a reel with teeth & a locking mechanism. When you pull the seatbelt in normal conditions, the reel allows the belt to get extended. In case of sudden braking or excessive jerking of the belt, the deceleration causes the locking mechanism to cut in & it prevents the reel from extending, thus holding you in your position.

Nowadays a few cars come with pre-tensioners & load limiters. A pre-tensioner is activated in case of hard braking and removes the slack on the belt, keeping you firmly in your seats. A load limiter on the other hand allows some slack in case of a high speed crash. This feature is present to limit injury caused due to wearing of a seatbelt. While stopping at high speeds, deceleration is very high. In that case, stopping your body instantly will do harm. A load limiter allows for some forward motion to reduce the amount of deceleration on your body thus reducing injury due to seatbelt.

ABS (Anti-Lock Braking System)

With ABS

abs 1

Without ABS

abs2

ABS prevents your wheels from locking in the event of panic braking. Not locking the wheels allows your car to be steered to avoid an obstacle while braking. Cars that don’t have ABS lock their front wheels under severe braking and don’t allow directional control.

An ABS unit consists of a wheel speed sensor, ABS control module, hydraulic modulator & a pump motor with an accumulator. The wheel speed sensor measures the speed of the different wheels and sends feedback to the ECU. When a wheel locks, the speed sensor detects the change in speed & sends a signal to the ECU to activate ABS. The ABS module regulates the amount of hydraulic fluid going to the brakes with the help of the pump and accumulator. In simple terms, it applies & releases the brakes at a rapid rate such that the wheels don’t get locked and you can steer the vehicle.

Airbags

airbag deployment

An airbag is a supplementary restraint system for the driver &/or passengers. It is a thin nylon bag that prevents the passengers from hitting  parts of the car. Depending on the number of airbags, its position varies. In India, most cars come with dual airbags (driver & front passenger).

There are 3 major components that make up the airbag unit- the airbag module, the diagnostic unit and the crash sensor. The sensor location depends on the number of airbags the car has. When an impact occurs, the sensor detects the deceleration and sends a message to the ECU to deploy the airbags. The diagnostic unit performs checks & monitors the readiness of the airbag at all times. It stores electricity to activate the airbag in the event of a crash. The airbag module has the nylon material as well as the inflator unit. The inflator unit has pellets that ignite to produce nitrogen gas. This nitrogen gas is what inflates the airbags so rapidly. Once the airbag is deployed, the whole unit needs to be changed.

Crumple Zones

crumple zone

A crumple zone is an impact absorbing area present in a car. Its location depends upon the design. When a crash occurs, a lot of energy transfer takes place. The crumple zone is made up of crash absorbing material that is designed to absorb as much energy from the crash and reduce the forces acting on the passenger cabin. The design of a crumple zone varies from car to car, company to company. Some use different types of metals to improve the absorbing capacity, others use basic frame to absorb the impact.

Collapsible steering column

steering collapse

The steering system is designed to collapse in a telescopic manner in the event of a crash. This prevents the steering from hitting the driver. The system comprises of a strong safety resin that holds the metal sleeve of the steering column in place. At the time of impact, the resin is designed to shatter thus allowing the steering wheel to move inside & not hit the driver.

 

Image source: 2