A question for those with little kiddies requiring child seats.

Previously I had a 4 year old Japanese car. When you pull the rear seat belts out fully, when you let it retract it clicks repeatedly and will not let you pull it out again until it is fully retracted. This is a safety feature when installing child restraints as there is absolutely no play in the child seat once you strap it in.

Question is, it seems most European cars do not have this feature, the mk5 Golf being one of them.

OK, I know in a crash situation the seatbelt pretensioner acts and will stop the child seat from moving. So is this any less effective than the type that does not let the belt be pulled out with the clickety thingy?