Lap and shoulder belts in the middle rear seats of vehicles will be mandatory under a bill headed to President Bush for his signature. But automakers say they've already begun installing the safety devices.
Until now, lap and shoulder belts have been required for the outer seating positions, but only a lap belt has been required for the middle.
Most child safety and booster seats are designed to be used with a lap and shoulder belt.
The rear middle seat is considered the safest for children in an auto accident.