The Seatbelt has proven to be by far the most important safety device in cars as it dramatically increases the chances of survival of the occupants in the event of an accident. It has been estimated that seatbelts reduce the risk of death for a front seat car occupant by about 50%. How does the seatbelt work?

Seatbelt's Principle of Working: When a car is speeding along at 50 Km per hour it has a tendency ('Inertia') to keep moving at the same speed and in the same direction unless some force acts on it. The car accelerates its occupants to its own speed so that they seem to be moving as a single unit. The inertia of the occupants is, however, independent of the inertia of the car. If the car were to crash into a tree, the force of the tree would bring the car to an abrupt halt. The speed of the occupants, however, would remain the same because of their independent inertia and they would bang into the steering wheel, the dashboard or the windshield. The force exerted by the steering wheel or the windshield would then bring the occupants to a stop but may in the process cause injury to vulnerable body parts such as the head and the face. The seatbelt's job is to spread this stopping force across sturdier parts of the body over a longer period of time to minimize damage.

A typical seatbelt consists of a Lap Belt, which rests over the pelvis and a Shoulder Belt, which extends across the chest. The two belt sections are tightly secured to the frame of the car in order to hold passengers in their seats. When the belt is worn correctly, it will apply most of the stopping force to the rib cage and the pelvis, which are relatively sturdy parts of the body. Since the belts extend across a wide section of the body, the force isn't concentrated in a small area, so it can't do as much damage. Additionally, the seatbelt webbing is made of a material having some flexibility so that it stretches a little bit thereby making the stop less abrupt. The softening of the crash by the collapsing of the crumple zones of the car also has the desired effect only when the occupant remains secured to the seat by the seatbelt.

Load Limiters: In severe crashes, when a car collides with an obstacle at extremely high speed, a seatbelt can inflict serious damage. As a passenger's inertial speed increases, it takes a greater force to bring the passenger to a stop. In other words, the faster you're going on impact, the harder the seatbelt will push on you. Some seatbelt systems use load limiters to minimize belt-inflicted injury. The basic idea of a load limiter is to release a little more excess belt webbing when a great deal of force is applied to the belt.

Law on Use of Seatbelt: As per the provisions of sub-rule (3) of Rule 138 of the Central Motor Vehicle Rules, 1989 'in a motor vehicle, in which seat-belts have been provided under sub-rule (1) or sub-rule (1A) of rule 125 or rule 125A, as the case may be, it shall be ensured that the driver, and the person seated in the front seat or the persons occupying front facing rear seats, as the case may be, wear the seat belts while the vehicle is in motion.

Rule 125 (1) requires the manufacturer of every motor vehicle other than motor cycles and three-wheelers of engine capacity not exceeding 500 cc, shall equip every such vehicle with a seat belt for the driver and for the person occupying the front seat.

Rule 125 (1A) requires the manufacturer of every motor vehicle that is used for carriage of passengers and their luggage and comprising no more than 8 seats in addition to the driver's seat, shall equip it with a seat belt for a person occupying the front facing rear seat.

As per section 194 B of MV Act-1988 (Ammemedment-2019):-
1. Whoever drives a motor vehicle without wearing a safety belt or carriers passengers not wearing belts shall be punishable with a fine of one thousand rupees.
2. Provided that the State Government may be notification in the Official Gazette, exclude the application of this sub-section to transport vehicles to carry standing passengers or other specified classes of transport vehicles.
3. Whoever drivers a motor vehicle or causes or allows a motor vehicle to be driven with a child who, not having attained the age of fourteen years, is not secured be a safety belt or a child restraint system shall be punishable with a fine of one thousand rupees.