I don't want to be trapped in a seatbelt. It is better to be thrown out of a vehicle in a collision….  
Being thrown free is 25 times more dangerous, 25 times more lethal. Is you are wearing your belt, you are far more likely to be conscious after a collision - to free yourself and your passengers. Seatbelts can keep you from plunging through the windscreen, being thrown out the door and through the air, scraping along the ground or being crushed by your own car. In almost any collision you are better off being kept inside the vehicle by seatbelts.

If I wear a seatbelt, I may be trapped in a burning or submerged vehicle….
Less than one-half of one percent of all injury related collisions involve fire or submersion. But if fire or submersion does occur, wearing a seatbelt can save your life. If you are involved in a collision without your seatbelt, you might be stunned or knocked unconscious by striking the interior of the vehicle. Then your chances of getting out of a burning or submerged vehicle would be far less. You are better off wearing a seatbelt at all times in a vehicle. With seatbelts you are more likely to be unhurt, alert, and capable of escaping quickly.

I don't need a seatbelt. In the case of a collision, I can brace myself with my hands……
At 50kph, the force of the impact on you and your passenger is brutal. There is no way your arms or legs can brace against that kind of force in a collision.

Some people believe it is a matter of personal choice to wear a seatbelt and refuse to wear one. How do you convince them otherwise?….
It is in fact law to wear a seatbelt. The refusal of a driver to wear his seatbelt can endanger the lives of other occupants, as well as his own. In the event of a collision, he can be thrown against another occupant, thrown onto the dash or windscreen, or out of the vehicle. The fact remains that your death affects taxpayers who have to pay to have your remains removed and they may also have to make a contribution to support your family. Your death affects your employer who has to find a replacement and has to train him. This cost is borne by customers in the form of higher prices. If you do wear a seatbelt you stand a better chance of retaining control of the vehicle and avoiding a secondary collision with a pedestrian or another vehicle. 

A good and careful driver does not have to wear a seatbelt…..
A good driver does not put other people at risk. Although you can control your driving, you cannot control the driving environment around you. You therefore need to protect yourself from inexperienced or irresponsible drivers.

How effective are seatbelts?
Most people accept the fact that wearing seatbelts offers protection in a collision, but too few bother to find out exactly how much protection they can expect. If they ask, they would probably be surprised by the answer. While researchers may differ by a few percentage points either way, average figures from seatbelt studies are as follows :
Seatbelts reduce the number of serious injuries sustained by 50%
Seatbelts reduce fatalities by 30 - 40%
In other words, not wearing a seatbelt doubles your chances of being seriously hurt in a collision. Serious injuries sustained during a collision often involve the head or spinal cord. In fact, in the USA, vehicle collisions are the number one cause of epilepsy (from head injury) and paraplegia (damage to the spinal cord). The restraining action of seatbelts - especially shoulder belts, helps explain why they so drastically reduce the likelihood of being seriously injured. 

Wearing just a lap belt gives you double as much chance of living in a collision as you would have if you wore no seatbelt at all. And using a lap/shoulder belt combination makes your chances of survival three to four times better. An important note - your chances of escaping injury or death because you are wearing a seatbelt holds true regardless of speed. Whether you are travelling at 10kph or 110kph, you are better off wearing a seatbelt. There is a "ride-down" benefit in which the belt begins to stop the wearer as the car is stopping. The belt keeps the head and face of the wearer from striking objects like the windscreen, interior post or dashboard. The belt spreads the stopping force widely across the strong parts of the body. Belts prevent vehicle occupants from slamming into each other.
Belts help the driver to maintain vehicle control, thus decreasing the possibility of an additional collision. Wearing a seatbelt can reduce your chances of being fatally or seriously injured in a collision by 40%.

Injuries in motor vehicle collisions and the role of the seatbelt.
Drivers of vehicles have more injuries on their left sides, and left-front passengers more right-side rib fractures. Among cases where the injury-causing impact was mediated by seatbelts, this difference is statistically significant. Professor Becker, a member of the University of Pretoria's Medical faculty says children often are thrown from vehicles and he feels there should be compulsory use of child restraints. Research has found that the death and injury rate of front seat passengers can be reduced if rear seat passengers wear seatbelts. About 5% of front seat deaths are caused by unrestrained rear seat passengers flying forward to hit the front seat occupants. Tests conducted by the SABS have clearly shown the dangers of not using a rear seatbelt. The test uses a 75kg manikin traveling on a seat on a trolley and colliding at 50kph against a solid object. The results showed that at this speed rear seat passengers without seatbelts could suffer serious or fatal head injuries. In a collision with a solid object at 50kph a seatbelt will keep the wearer in position with a force equal to thirty times his mass. An unrestrained occupant would have to exert this same force (2250kg for a 75kg person) to prevent being catapulted out of the seat. The force required equals the weight of two cars or the weight of 29 people. The fact that the rear seat passengers are seated further away from the front of the vehicle tends to give them a false sense of security. It is however, just as important to wear seatbelts in the rear as in the front. Both front and rear seat passengers not wearing seatbelts will most likely be flung through the windscreen in the event of a front-end collision. In rear-end collisions, passengers can easily be flung head first against the rear window and in extreme cases, right through it. When vehicle occupants wear their seatbelts in a collision, they can break bones, damage their chest bone or spleen, or tear their liver. Injuries are however, much more serious when not wearing a seatbelt. Typically, front and rear seat passengers, not wearing seatbelts, sustain brain, internal, chest, abdominal, heart, liver and facial injuries as well as injuries to the spleen. This clearly illustrates that the fear of some people of being seriously or fatally injured by wearing their seatbelts is not justified. If you are travelling at 50kph and are involved in an accident you would be thrown forward at a force equal to thirty times the weight of your body. Say you weigh 70kg, which is the average weight of dummies used to test cars, and you traveled at 50kph and are involved in a collision, you would travel forward at a force equivalent to 2.1 tons. If you were travelling at 100kph, a more appropriate speed for South African roads, the force would increase to 4.2 tons.