Using the old regulations, ECE R44/04, which are still in force until 2018, the tests basically consisted of longitudinal testing: a head on collision test at 50km/hr., to measure the displacement and the force exerted on the body of a child (head, neck, chest…), and a rear end crash test at 30km/hr.
They also included various tests on the seatbelts or harnesses, to check whether they could be safely adjusted for use by children, whatever their size and weight, as well as on the harness buckle, to establish whether it could be easily opened after an accident.
As well as this, they checked that the seats had no unprotected sharp edges or rigid parts, the behavior of the materials from which they are made in a fire, the resistance of the metal parts to corrosion, the toxicity of the components, etc.
The new ECE R129 regulations, also known as i-Size, are now in force and coexist with the old ones; although there is now an increase in the tests that the child seats have to pass. The main one is that a lateral crash test is added. In both cases the force that the head and thorax are subjected to during a crash is tested.
They also perform tests on the way that the materials absorb the force of a crash, the harness tension and the strength of the third support point known as the top tether or the foot.
In Sweden, they have another test of their own, in addition to the International Regulations, called the Plus Test, which is voluntary and not obligatory. That is to say, a seat can be sold there if it complies with the European Regulations, but if they want to show a higher certification and better safety standard, the seat can be tested using the Swedish test to obtain the corresponding approval stamp. Parents do take into account, whether a seat has passed this test.
A notable difference is that the speed of the deceleration of the seat and the child in the Plus Test is much higher, that is to say that the seat undergoes much more severe testing.
As well as testing the force to which the head and the thorax are subjected, they test the force to which the neck, the most fragile part of a small child is subjected.
If this wasn’t enough, the limit of maximum force considered to be tolerable, is lower. This signifies that passing the Plus Test is very difficult, so the seats tested and approved are even safer. Some of the seats awarded this certification are, Römer Max-Fix II, Britax Max-Way 2015, Axkid Minikid y Rekid, Klippan Kiss 2, Besafe IZI Plus y IZI Kid X1.