Pennsylvania motorists will have to make sure car seats face backward for all children until they’re 2 years old under a new state law that goes into effect this week. The measure that becomes law Friday directs police to issue warnings for the first year, after which violations will cost $125 in fines, costs and fees. Pennsylvania is the fourth state to enact the rear-facing child seat regulations for the youngest of children, after California, New Jersey and Oklahoma. Backers of the new child seat rules say facing children toward the back of the car dramatically lowers their risk of death or serious injury during crashes. PENNdot says children should remain in rear-facing seats until they reach the manufacturer’s height or weight limits.