SEAT BELT LOCKING MODES
In some vehicles, the lap-and-shoulder seat belts have two modes of operation: Emergency Locking Retractor (ELR) and Automatic Locking Retractor (ALR). The ELR mode (normal mode) allows the seat belt to freely extend and retract to allow the passengers some freedom of movement in their seat, yet locks the seat belt during a sudden stop or upon impact. The ALR mode (child restraint mode) locks the seat belt for child restraint installation. When the ALR mode is activated, the seat belt cannot be extended again until the seat belt tongue is detached from the buckle and fully retracted. The seat belt returns to the ELR mode after the seat belt fully retracts.
In the US, where it's legal to install a child restraint using only the vehicle's seat belt, all cars made after 1996 must have seat belts which can switch into ALR mode. In Singapore, however, where child restraints in private vehicles must be installed using an anchor, vehicles with ALR-enabled seat belts are not common.