Car’s isofix


If you’re thinking about buying a car, or even a Child Restraint System (CRS), this is the post for you… in case you didn’t know, not all cars are able to accommodate the ISOFIX anchor system, and not all child seats are compatible with this system. Without the ISOFIX anchor system, your children’s safety cannot be guaranteed to any suitable degree for reasons related to installation.

Any vehicles manufactured since August 2010 have been legally required to include ISOFIX anchor systems (we will look at this point more closely later on in the post); however, some second-hand cars over a certain age may not have ISOFIX anchor points as their installation was not required by law at the time of manufacture. Moreover, as indicated above, not all Child Restraint Systems are adapted to this kind of ISOFIX anchor system. It is best to check before you purchase one. It is very common for a car to have two isofix shackles but not a top tether shackle, in which case a child seat with isofix and top tether cannot be fitted.


This anchor system which universally or semi-universally governs the installation of a child seat has German seal of approval. It was established 21 years ago, in 1997 to be precise, by Volkswagen and Britax Römer, who produced the first prototype. This prototype was devised at an earlier stage and its creators intended to present it at the International Motor Show (IAA) of Frankfurt (Germany) for the Volkswagen Golf IV car model. Its true origin goes even further back, as discussed at greater length at the end of this article.

What is the isofix anchor system?

It is a two or three-point anchor system which makes it easy to attach the child seat to the car; it increases safety and secures the child seat or child restraint system to the vehicle’s chassis. The fact that it increases safety and is easy to install reduces the risk of serious injury and, of course, the death rate in the event that the minor is involved in an accident.

The name of ISOFIX comes from ISO (International Organization of Standardization), which is responsible for establishing and formalising international standards.

With that in mind, the ISOFIX anchor system is duly recognised for the major contribution it makes to the safety of our children during car journeys.

(CAISA, Consultoría Aeronáutica Integral S.A.)

Any child under 135 cm or 150 cm high, depending on the country, is required to use an approved Child Restraint System whenever they travel by car. The use of such a system is recommended until they reach a height of 150 cm. Of all CRS, the ISOFIX anchor system is regarded as one of the most successful on account of three key concepts: easy installation, quick installation and benefits. This is demonstrated by the fact is that the most recent international standard (ECE-R129) for the manufacture of CRS makes it “compulsory” in its first two phases. Phase 3 of the ECE R129 (i-Size) approval has been extended to include the possibility for child restraint systems with a safety belt to be approved.

What are the components of the ISOFIX anchor point system?

As it is a connection system between two elements, its components are attached to two elements (car and child seats for the car):

The vehicle has 6mm diameter shackles which are separated by minimum intervals and can be used by another element for connection purposes. The isofix, commonly known as isofix shackles, can be welded or screwed to the vehicle chassis via a steel sub-chassis. They can also be built into the car’s seat.


Most were originally welded to the chassis and, in recent years, in light of the fact that seats are able to move in a very flexible manner within the compartments, shackles now tend to be built into the vehicle’s seats. Incidentally, the distance between the side of the car and the first shackle is not regulated by any standard and depends simply on the vehicle manufacturer.

As for the child seat, booster seat, child restraint system, etc. the isofix is a “more complex” component which uses a “connector” to attach the seat to the vehicle. There are various kinds of isofix connectors available on the market. Although they all have their own different exterior geometrical characteristics, their interior geometry is precisely defined in accordance with the international standard.

There is a third anchor or anti-rotational point both in the car and on the child restraint system. It may take the form of a top tether, support leg or even a safety belt.

What purpose does the ISOFIX anchor point serve?

You must have wondered what makes the ISOFIX anchor point the most successful system in the childcare sector… Well, it is the only system whereby the child seat is completely fixed to the vehicle with the vehicle chassis being securely attached to the chassis of the CRS. Otherwise, the child seat would sit on top of the car’s seat attached by the safety belt.

Moreover, most child seats currently available on the market have the ISOFIX anchor point which is why, though you have to check before buying the child seat, it is actually difficult to come across one that is not suitable. Ask your seller, but remember that guidance can also be found in the car seat’s user instructions.

On the other hand, when we talk about the ease of using the system, we are referring to its installation: as it is easy to fit the child seat onto the anchor points, it won’t take you long… we also provide a guarantee that the child seat will be installed correctly. It is particularly important to correctly install the child seat because, at times of increased strain, e.g. an emergency stop or a collision, it optimises the degree of protection afforded to the baby.

It is important for child seats to be correctly installed; as part of the various research studies carried out by RiveKids, we have conducted impact tests with incorrectly installed child seats and the findings are conclusive: An incorrectly installed child seat fails to provide protection and it may occasionally present a danger for all other occupants of the vehicle.

The various groups of child seats and the ISOFIX anchor point

The ISOFIX anchor point system is the most appropriate for child seats from groups 0, 0+ and 1, for children up to 18 kg in weight or 105 cm in height (approximately) and, of course, also for their counterparts under ECE-R129.

In respect of these groups, child seats with ISOFIX are required to have a third anchor point which complements the ISOFIX and further guarantees the degree of protection afforded to babies and children. The third anchor or support point means that the child seat does not rotate in the event of a head-on collision, and is classified into two categories:

What is known as top tether, consisting of a safety belt which fixes the rear part of the seat to the rear of the car seat’s back. This has been compulsory in vehicles manufactured since 2013 although it was present in vehicles long before that.


It should be noted that a three-point child seat should not be fitted in any vehicles that do not have a Top Tether due to the risk of “overturning”. Not all shackles of the boot are valid. The boot must have an anchor point and be identified by the name of Top tether.

In this case, you will find the following option to be more appropriate.

If our child seat does not have this third anchor point, there is an extra anchor point or support leg which further secures the attachment of the child seat to the anchor point because it will stop the car seat from overturning in the event of an accident. Provided that the support leg is correctly installed and is able to be fitted to the base of the car, it will help to guarantee the minor’s protection. The upholstery of vehicles does not contribute to safety and, in the event of a head-on collision, a child seat without a third anchor point will tend to rotate to a degree determined by the dimensions of the vehicle’s upholstery.

We then have the seats from groups 2 and 3 and their counterparts under R129, which include ISOFIX combined with a safety belt. Manufacturers of child seats change the name to ISOCLIC, ISOFIT, etc. and, although it is not compulsory, it is indeed recommended. As for seats from group 2 and 3, approved in accordance with ECE R129, the name of isofix is retained.

The effectiveness of ISOFIX or similar mechanisms from groups 2/3 is demonstrated by the decision of most brands on the market to fit these attachments into their models despite the fact that they are not compulsory. Incidentally, the Spanish brand Jané was the first to install ISOFIX onto a group 2/3 child seat.

The use of rear-facing child seats is recommended until our children reach 18 kg in weight or 105 cm in height, and we endorse this recommendation; from that time onwards, we must continue to protect our children and we can do so by using 2/3 seats, always with head support and protection.

How is a child seat with ISOFIX anchor point fitted?

As indicated above, the use of the CRS, adapted to the size and weight of the child, reduces the death rate by 75% and the likelihood of suffering injury by 90%. This protection is only guaranteed if the child seat is correctly installed. The ISOFIX anchor point makes this process much easier. An incorrectly installed child seat causes or may case neck, head, chest or abdomen injuries to our children in the event of an accident.

You should read the manufacturer’s instructions to ensure that that child seat is correctly fitted. After reading them, if the child seat has ISOFIX, the two anchor points of your child seat should be attached to the two shackles on your car’s seat (they are usually located on the rear side seats or are sometimes found on the front passenger seat in some models. However, if your child is to travel in the front passenger seat on account of the fact that the rear seats are already occupied by children of a younger age, you must deactivate the front airbag).

If a group 0/1 or similar child seat is used, the top tether or support leg must be installed.

For group 2/3 child seats, the car’s headrest must be at the same height as the child seat’s headrest. Otherwise, your child is not protected in the event of an accident.

You will note that the child seat is effectively attached but is not perhaps as rigid as you were expecting. That is completely normal. The minor movement is beneficial as, if an accident occurs, the child seat needs to support the baby on impact, instead of being completely rigid. The tolerance levels established under ECE R14 for car manufacturers and under ECE R44 and ECE R129 allow for a slight sideways movement which is made possible by the movement of the connector (CRS) along the shackle (vehicle).

Is a child seat safer with isofix?

It is fundamentally safer for two reasons: It guards against incorrect installations and it is able to absorb energy in the event of an accident.

The three-point inertia-reel safety belt is now installed in all vehicles worldwide; it is a basic safety device designed to protect adults. Isofix is a safety device whose original design aimed to protect children in their child seats or child restraint systems.

A child seat is able to protect the child by reducing the death rate by 75% and the likelihood of suffering serious injury by 90%, provided that it is correctly installed in the car.

The safety belt needs to be manually tightened both for use by adults and for use with car seats; however, isofix has a simple correct installation indicator unlike the safety belt.

Advantages of the ISOFIX anchor point in the car

Isofix makes sure that the child seat (CRS) is correctly installed. Several studies show that, by and large, if a car seat is incorrectly installed, in most cases, but not all, the seats tend to be installed with a safety belt. The car and seat manufacturer’s instructions must be read carefully to guarantee correct installation.


Did you know that car manufacturers also determine the seats onto which child seats may or may not be fitted? We give you some examples of the most widely sold vehicles throughout Europe.

With the car and seat isofix, installation is quicker, easier and comes with a correct installation indicator.


In a society where children often travel by car, with friends, with trainers, with family members, etc., a simple, fast and effective system is essential to guarantee their safety, irrespective of the kind of car journey involved. All these characteristics are provided by the car’s isofix when it works in conjunction with the seat’s isofix.

Isofix improves the biomechanical values in the event of a side impact. A seat with isofix in a car with isofix is able to increase protection for the minor as it absorbs part of the energy generated by the deformation of the steel with which the isofix mechanism is made.

As parents, we think that the isofix on the seat is the most important element and that the car’s isofix is a mere shackle. Nothing could be further from the truth: the positive effect is provided by the connection between the two elements.

The car’s isofix and the seat’s isofix are securely connected to each other, although not rigidly so, and the seat’s adjustment on the car seat will depend more on the upholstery than on this connection. We tend to think that the car’s seat has to be rigid during installation. However, the car’s isofix ALWAYS allows sideways movement, to one extent or another, depending on the car make and the child seat model, but there is always sideways movement. For front-facing seats, there is also some tolerance, but in this case we are talking about a few millimetres and it is less noticeable. As in the case of isofix, two elements are not able to universally connect unless there are tolerance levels which allow for such a connection.

The car’s isofix is much more than a shackle welded to the vehicle’s chassis or to the seat’s structure. The car’s isofix increases safety in the event of any kind of collision with child seats.

If the car turns over, the car’s isofix will be securely attached to the chassis and will allow the seat to move, although to a lesser extent than a seat supported by a safety belt. The safety belt is a flexible element whose inertia-reel is quite distant from the vertex, between the back and the seat, which may cause greater movement, in the event of an overturn, than a seat with isofix which does not allow flexibility beyond the point offered by the seat and the vehicle’s upholstery.

In the event of a head-on collision, the car’s isofix will remain securely attached to the seat via the vehicle chassis and will allow all the energy structurally absorbed by the rear of the vehicle to benefit the child seat or child restraint system. The car’s isofix will make it possible to match or resemble vehicle and seat decelerations, thus improving the biomechanical values in the event of an accident. In the case of child seats for older children, the minor will not be propelled sideways and the safety belt will only support the minor and not the unit (child + child seat) which is what happens if the seat does not have isofix or similar anchor points.

In the event of a side impact, the car’s isofix “practically performs miracles”. The car’s isofix allows a secure attachment between car and seat, albeit with minor relative movement. In the event of a head-on collision, the isofix will make it possible for the child seat, working in conjunction with the car, to absorb part of the energy. Firstly, if there is no panel/door penetration, the car’s isofix will limit the rotating effect of the child seat and the sideways movements that the safety belt is unable to absorb. Secondly, if there is panel/door penetration, the combination of the car’s isofix and the child seat’s isofix can absorb energy due to the deformation of the car chassis steel in the isofix area and the child seat chassis steel in the isofix area; even the isofix connector may bend by absorbing energy due to the deformation of the steel. The steel, aluminium and alloys of the chassis of the seats and vehicles allow much of the energy to be absorbed due to deformation. In the same way as the vehicle nose gradually “wrinkles” and absorbs energy, other parts of the car or seat chassis gradually “wrinkle” and absorb energy. If these elements were too rigid, they would transmit energy and would not have any absorption capacity. Vehicle chassis are designed to absorb energy by the controlled deformation of steel.


As you will already know, we at RiveKids are fully committed to ensuring road safety, and in particular child road safety. That is why our RiveMove technology is compatible with many of the child restraint systems characterised by their ISOFIX, ISOCLIC, ISOFIT or similar mechanisms. If you would like any further information, please feel free to contact us at


R44/04 and R/129 i-Size Approval

As far as regulations are concerned, there are two approval standards

R44/04, valid since 2006

R/129 (I-Size), valid since 2013 and co-existing with the previous standard for a period in which manufacturers, distributors and consumers will be required to adapt to the requirements thereof.

The main difference between the two approvals is that, where seats were previously categorised by weight and age, they are now classified by height and weight. Moreover, the latest standard includes a compulsory side impact test without which approval is not granted (homologation); this was not previously a requirement and it is a very welcome addition as it serves to improve safety. It should also be noted that the biomechanical values required under the latest standard are more stringent. Whereas P dummies were previously used, Q dummies have taken their place as they are the most advanced in terms of the instrumentation used to measure biomechanical values.

How do I know if my car has an ISOFIX system?


Since 2004, most, if not all, cars in Europe are characterised by an isofix mechanism fitted to their rear seats. There has been exceptions during this period where the isofix is present albeit as an extra, as in the example of the Ford Focus, the Audi A4 or any model produced by Volvo.

In actual fact, since 1997, isofix technology has been released onto the market very quickly and, even before 2004, this serial or extra anchor point had been installed in most cars.


How do I know if my car has an isofix system? If it was manufactured after 2004, it is very likely that the car will include the serial anchor point; it is best to visually or manually check the car itself. If your car was manufactured after this year and does not have an anchor point, you will almost certainly have the option of adding one as an extra.

At present, information about anchor points is included in the instructions of most cars. However, it is best to personally check that it is there; you can refer to the instructions to ascertain its location. The following video reveals how to check whether your car has an isofix system, where to look for it and also how to identify the top tether.

Are any accessories used to install isofix into my car?

We are absolutely delighted that some readers of this article have contacted us at to put their questions to us. We also share photos taken from ebay of isofix accessories for numerous models of the car; the idea is not that you should purchase the isofix for your car on this platform. It is merely to give you examples of the specific accessories available and their reference for your isofix.


What is the origin of ISOFIX clamping system?

After delving deep into the archives, in the knowledge that if we did actually find anything, it would no doubt be relatively unknown, we came across a Swedish study originally called ‘ISOFIX – A New Concept of Installing Child Restraints in Cars’ published in 1994 and regarded as the first known reference made to ISOFIX.


This document, produced by the authors Thomas Turbell, Richard Lowne, Björn Lundell and Claes Tingvall sought to address the usual and incorrect way in which CRS are installed in vehicles. However, this study did not seek to minimise damage or reduce the likelihood of injury to the occupants of seats, i.e. it was not a study into passive safety as such. A much simpler explanation than the above is that ISOFIX, at least according to the description of the aforementioned document from 1994, only aimed to facilitate the overall installation of all seats into the car on the basis of a new anchoring system.


The following text is taken from that study:

“One of the main problems of CRS is that they are used incorrectly or are simply not used on account of installation conditions. To resolve this issue, in 1990 the Swiss delegation at the ISO group began to produce the first prototypes of an “ISOFIX” system which would specify the anchoring system between the car and the CRS. The ISO group is assessing various concepts and a preliminary draft of a new ISO standard is expected to be ready by 1994. Although the “ISOFIX” cannot be included in the present update of Regulation ECE R44, it will be promptly incorporated just as soon as it is ready.”

This document therefore represents part of the origins of a technology with which we are relatively familiar and which, if truth be told, has not been altered to any significant degree in recent years. But, naturally, the technology was altered in the early days and alterations to the design were often considered. But this document precisely addresses that point: the prototypes presented by the various manufacturers and companies and the numerous proposals put forward to resolve the issue.


It would therefore be useful to study this publication as the document represents a comprehensive source of alternative models to the ones we know today as the ISOFIX anchor point.

Predecessors to the ISOFIX anchor point

Below are four designs that were presented to the ISO Child Restraint System group (ISO/ TC 22/SC 12NVG 1) in 1990:

As you can see, the first prototype (Fig. 1) involves a two-point system based on two threaded pipes connected to each other. This model dates back to 1991.

There are many others such as, for instance, the DELTAFIX system (Fig.2) presented by AUTOLIV also in 1991, which this time consisted of a three-point design and which afforded greater stability and a greater distribution of force. The third model (Fig.3) was a simplified version of the DELTAFIX system inasmuch as it only used two anchor points.

A special mention is reserved for the final model displayed in the image as it is actually a very close approximation of the current ISOFIX system. Known as

UNIFIX, according to the study, this design is a joint effort of manufacturers and researchers from the UK.

It is characterised by two rear anchor points between the base of the restraint system and the vehicle. These anchor points consist of 2 x 6mm diameter steel bars. While the front part requires one more point to completely secure the CRS to the car seat.

More models were presented to the ISO group, all of which are featured in the original document. This document not only looks at the models shown, but also sets out a list of requirements prior to the time when new forms of innovation and designs were accepted. Any newly developed system was obliged to meet these requirements before it could be contracted and compared with all its other counterparts.

The Swiss authors divided the list of characteristics into “Essential Characteristics”, “Highly Desirable Characteristics” and “Good Characteristics”. As the initiative sought to simplify the vehicle anchor method and to increase the ease with which these systems were fitted into cars, it favoured a system that was simple, included a mechanism to guarantee that the device had been correctly installed, universal (valid for all CRS), did not become loose in an accident and characterised by a whole array of other features that would be considered by ISO in the presentation of the project. The following image displays one of the aforementioned lists.

Now that you have read this article, you have no excuse not to use an appropriate child seat! And remember that it is vital to set a good example: as adults, you should always wear a seat belt and respect highway code regulations. These practices cost you nothing!

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