The first seat belt laws were for drivers only, where the argument was that in a crash, the driver bangs their chest against the steering wheel; and a seat belt would hold the driver in place and prevent a very serious injury to the rib cage. Seat belts were made compulsory for drivers of all cars. However, passengers in the cars, even in the front, were not required to wear seat belts, because they do not have a hard object, the steering wheel, right in front and so close to them.
The safety experts saw the success of their publications and latched on to the idea. The standard argument used by this group of people is "you can never be too safe". Since they could convince government agencies that a seat belt was a good idea for drivers, they created more studies and data to show how seat belt saved lives and prevented serious injuries not just for the driver, but for the front seat passenger as well. In a few years, the government agencies made seat belts compulsory for front seat passengers as well.
Fast forward a few years and the logical next step was to create data and statistics to prove how much it would benefit if we forced the back seat passengers to wear seat belts. Seat belts were made compulsory for all four passengers.
Somewhere along the line the simple waist belt was thought to be too little protection-and larger belts which run over your shoulder in addition to tying you up at the waist were made compulsory.
An astute researcher (or a company) saw this and said that the children were not tied into the seat belts very firmly; they invented a baby seat. The purpose of this seat was to tie a baby very uncomfortably into it; and since man loves babies more than adults, the governments quickly fell for this data and made it mandatory that all babies ride in these seats. Even mothers who wore seat belts could not carry their babies in their laps; they had to tie up the poor baby next to her in the baby seat.
Airbags were made compulsory in cars in late 1990s. Some children in the front seat died because of the airbags opening on them (faulty airbags, small shocks, etc). The irony of a feature which itself kills people was completely ignored. Faulty airbags are a constant source of injuries even to adults.
To prevent airbag related child deaths in front seats, the government agencies made it mandatory that all children below 8 years of age be carried only in the back seat of the car. If they were babies less than 3 years old, they were tied into baby seats; if they were more than 3 years old, they could sit in the back seat, but always with the seat belt on. The natural desire of a parent to have a child at her side was sacrificed to the "scientific" judgement of the safety experts. Many babies have died because the parent left their car in a hurry and forgot that they had the baby with them (you would not forget if the baby was in the front seat, but you are much more likely to do so if the baby is in the back seat and sleeping). Once again, a rule which probably killed more babies than it saved (babies in the back seat, tethered to a special baby seat) has been instituted as a requirement for drivers.
Even if your car doesn't have an airbag, someone thought (and proved with data) that babies in these baby seats and children were still not safe in the front. So they were forced in the back seat for all cars.
All this has happened between 1980 and 2017 (I am writing this in 2017), in a span of about 40 years. Essentially, every 10 years, there has been a major safety regulation forced upoin people by governments worldwide.
Flaws with these studies
How is this data taken? I looked at several of these studies, which proved that seat belts saved lives, etc.. The studies have major flaws in them. I will not criticize the data study by study, but the major problem with many studies is that car accidents have so many different variations in real life, that very little good conclusions can be drawn from looking at just a few of those accidents. Others are full of simulated conditions in a test lab, which have not much to do with the extremely large number of different real life accident scenarios.
I also don't see any logic in putting seat belts on heavy trucks and buses. I can't imagine a major accident with such heavy vehicles where a seat belt will save the driver's or the passengers' lives. The vehicle itself is their best protection. If the vehicle can't protect them, I don't think a seat belt can.
The vehicle is also a major protection for the driver and the passengers for smaller cars. Adding a little bit of extra protection with a seat belt or an air bag doesn't change the probability of dying or serious injury, in my opinion. The only exception would be for the driver with a steering wheel-with the risk of the steering wheel hitting her ribs. For future cars which may not have a steering wheel, a seat belt for even the driver is not necessary.
Or, if we continue on the safety bandwagon, to play the devil's advocate-I think the next step would be to put helmets for all passengers in cars. Let's take it even further-why not extend helmets to people walking on the road as well? Or better still, let's just have custom metallic iron-man style suits for everyone, and in the morning when we get up, we should be compulsorily made to put an iron-man suit which is all body protection. You obviously need to get a custom iron-man suit for each of your children. So the future of humanity will be everyone dressed in metallic iron-man suits walking around safely, riding their cars safely, and the little kids will be going to school in their iron-man suits so that they cannot be harmed by any accident at all! I am sure we will have future researchers showing how much safer we become by all these things. You can make up data to suit your needs. Formula 1 (F1) drivers put seat belts, a helmet and iron-man style suits-to keep themselves safe. But there's no need to subject the general public to this as a rule, because F1 races have a very high probability of accidents, unlike real life. The way we are going, it seems the F1 suits will be the norm for all of humanity, in the name of safety. Hey, you never can be too safe, the safety experts say.
Wearing a helmet will certainly improve my safety-but is it worth it? The probability of someone hitting her head in her adult life is rather low, and the discomfort of having a helmet on at all times must be weighed carefully against this probability. Because this probability is low and difficult to calculate (notwithstanding the researchers who will come up with something anyway), it is better for the government agencies to not make laws for these low probability events. If an individual decides to walk around all her life with a helmet, it is her choice; but there's no need to make it compulsory for everyone.
If seat belts were as beneficial as they like us to believe, you would see a massive collapse in deaths and injuries once seat belt laws were instituted. You do not see this-the number of deaths remains about the same (with its natural variation) and the institution of seat belt laws has not lead the significantly less number of deaths for adults and children. The argument that they would be even more if you didn't have these laws (figures say they would be between 10% and 100% more...basically come up with random estimates) seems bogus to me, because of the reasons mentioned above.
I was in Osaka, Japan recently, and enjoyed how mothers would ride bicycles with their babies freely in the suburbs of Japan without helmets on themselves or their children. Japan has one of the highest life expectancies in the world, if not the highest. Clearly if they are able to do this, we should realize that bike helmets are not necessary, and should not be made obligatory. If people decide to put them on it is their choice.
Takada, one of the biggest makers of air bags, had to recall millions of vehicles worldwide because of faulty airbags. I will deliberately not quote the data there which led the highway authorities to conclude that the bags are faulty-but it is sufficient to say that a feature which was designed to save lives may also causing deaths. While it is true that if the number of deaths due to faulty airbags were much lower than the number of lives saved due to the airbags, we may support airbags, but as I have said earlier, the "evidence" as to how many lives air bags have saved is rather inconclusive. Absent this, to put a fairly complicated piece of equipment which doesn't work properly all the time, the air bag, inside the car sounds like a bad idea to me. Air bags are also additional cost to everyone-the more unnecessary safety features are added to a car, the more the costs go up.
Note that these are completely different from rules made to prevent someone drunk driving a car. They risk the life of other people on the streets if they drink and drive, and rules against drunken driving are good for society. Even though a drunk driver has a low probability of getting into an accident, the very fact that they can harm other members of the society makes it necessary that they be restrained from this behavior. However, if they drink themselves silly and fall off their porch it is their right; and the government does not need to make rule for that. You have the right to hurt yourself, but not other people.
In summary: Seat belt rules, baby seat rules, children in the back seat only, air bags, helmets, etc. are unnecessary rules by an over-eager and overreaching government. The data is fudged, inconclusive, and cannot be relied upon because it does not simulate real life conditions of how accidents happen in real life in thousands of different ways-and these protection and safety features must be decided by people at the individual level, not shoved down people's throats by a government agency.