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Seatbelts are seen by nearly most safety experts as devices that increase chances of survival in a crash. As per National Highway Traffic and Safety Administration reports, 13,000 lives in the United States are saved every year by seatbelts. NHTSA findings also suggest that chances of a fatal accident are reduced by 50 percent if the occupant wears a seatbelt.
Crashing basics:
Every object in the car including the people in it has inertia of their own which is different from that of the car. However, the car speed and the riders speed ultimately become the same and therefore both move as a single entity. Now, imagine a scene where the car were to hit an object, the car would stop suddenly, however you would still be moving at the same speed as your inertia is different. Not having a seatbelt would mean that you would either bump into the steering wheel or go flying through the windshield at the speed at which the car was traveling.
It must be understood that in event of a crash, a force is exerted on you to slow you down. However, the difference between life and death comes from how and where the force is exerted. For instance, if you crash into the windshield with your head, the stopping power is focused on one of the most susceptible regions of your body. Also, as glass is hard it stops quickly thereby increasing the chances of a fatal or severe injury. A seatbelt comes into picture by transferring the stopping force to stronger areas of the body and for a longer duration.
How a seatbelt helps?
A regular seatbelt comprises of a lap belt, which lies on the pelvis and a shoulder belt, which covers the chest. These two belts are firmly secured to the car’s body to prevent riders from falling from their seats. On wearing the belt properly, majority of the stopping force is applied to the rib cage and the pelvis, which are comparatively stronger body areas. As the belts stretch over a greater part of the body, too much damage is prevented.
Extending and retracting:
Seatbelts have a property that enables them to extend and retract, allowing you to bend forward although the belt is reasonably tight. The usual seatbelt system comprises of belt webbing which is in turn attached to a retractor mechanism. A spool found at the core of the retractor is connected to one end of the webbing. Within the retractor, a torque is applied to the spool, thus rotating it to wind up extra webbing. In the event of a collision, the spool is prevented from rotating by a locking mechanism present within the retractor.
Two types of locking systems are used in today’s cars:
· systems triggered by the belt's movement
· systems triggered by the car's movement
The Pretensioner:
Modern versions of seatbelts contain a system called pretensioner that also helps to tighten the belt webbing. A pretensioner’s purpose is to make the belt webbing tighter in case of a collision. Pretensioners usually co-ordinate with conventional locking mechanisms, rather than substitute them. Several varieties of pretensioner systems are available today including ones that contain electric motors or solenoids; however the ones with the greatest demand are the ones that use pyrotechnics.
Load limiters:
In cases of extreme crashes, seatbelts with load limiters help to reduce injury caused by wearing the belt itself. The most basic types of load limiters have a fold stitched into the belt webbing. More sophisticated load limiters contain a torsion bar in their retractor system.
Results have shown that seatbelts get the highest priority as safety devices in cars and trucks. However, they are not foolproof and their design can be enhanced further. The cars of the future are likely to have better belts and probably entirely new safety mechanisms. The biggest challenge of the government, though, is making people use these systems.