The Swedish Transport Institute (VTI) perform a car seat crash test called the Swedish Plus Test. Its predecessor, the T-Standard Test was first developed in 1975, seven years before R44 car seat tests were mandatory in Europe. This makes Sweden the world leaders in car seat testing.
The Swedish Plus Test is a frontal impact carried out at 56.5kmh/35mph which uses a shorter braking distance than other tests, making the impact even more severe. It is the only car seat crash test in the world that measures the loads on the child's neck. In all forward facing car seats the loads on the neck are higher than the safe maximum. This is why only rear facing car seats can pass the Swedish Plus Test. Car seats that are forward facing or have a forward facing option are not tested because they are not expected to pass.