What they are and what they do
A seatbelt is a type of restraint made of thick and flexible material, such as polyester. It acts as a crash avoidance feature, as it provides protection to the occupants of a car during an accident by securing them to the car. Without seatbelts, it is possible that occupants of a car could be thrown from their seats in the event of an accident. According to Daily Journal, “ejection happens in nearly 25% of all car accidents” because of lack of seatbelts. Seatbelts have been found to lower the risk of fatal injury to front-seat passengers by 45%, and for this reason they are now standard in all cars made around the world.
How they work
In the event of a crash, the mechanics behind the seatbelts will pull taught in order to keep passengers in place. The main purpose of seatbelts is to help prevent the impact of inertia on the human body. Newton’s law of inertia states that, “an object in motion continues in motion with the same speed and direction unless acted upon by an unbalanced force”. This means that if a passenger in a crash was not wearing a seatbelt, they would continue to move forward at the same speed as they were travelling with the car in motion. For example, if a car was travelling at 60km/h and was then involved in a crash, the passenger would continue to travel at 60km/h if they did not have a seatbelt to hold them in place.
Instead of the passenger and vehicle being separate objects, a seatbelt effectively makes a passenger part of the car itself. So, if a car were to crash, the passenger would be very unlikely to be ejected if their seatbelt was worn properly.
Development
Nowadays, the most commonly found seatbelt is the three-point seatbelt. This type of seatbelt is attached to the vehicle’s interior in three different places (refer to diagram on right): above the passengers shoulder (point A) and on either side of the hips (points B and C). This means it secures the passenger across the chest, shoulders and pelvis. In the event of an accident, this seatbelt will help to distribute the car’s stopping force across a large section of the body to reduce the likelihood of serious injury.
Before the three-point seatbelt came in to use, seatbelts were made with only two points. These points were on either side of the hips (points B and C on diagram on right) and were not very affective in preventing injury. These seatbelts still allowed for the passenger’s torso to be thrown forwards, and they did not effectively distribute the force of the car’s impact, meaning many people suffered injuries that are not as common with the use of three-point seatbelts.
The latest advancement in seatbelt technology is the inflatable seatbelt, which Ford included in their Ford Explorer model in 2011. These seatbelts are only included in the rear seats of a car, with the aim of acting as an airbag that is safe for children.