A child must be 40lbs to sit in a booster seat by Oregon law... You can get convertible seats at Big Lots for $40 or Wal-mart. Below is a copy of the law with a good resource for child safety seat questions. It is too bad that boosters say you can put a child in them before they are really ready.
Oregon's Child Passenger Safety Law Changed
Oregon law assists drivers in the decision of how to properly restrain and
protect children in motor vehicles. When children are properly restrained it
significantly decreases the severity of injuries and number of fatalities that
occur in a crash. The recent amendments to Oregon¹s law now reflect national
best practice.
Infants must ride rear facing until they are one year old and twenty pounds.
Before children can ride forward facing, they must meet both of these benchmarks.
Once a child has reached a minimum of forty pounds they must be properly
secured in a booster seat until they are eight years old or are taller then four
feet nine inches.
After a child is age eight or older, or they are at least four feet nine inches
they must be secured properly with the safety belt system.
The law continues to require:
Children over one year old and between twenty and forty pounds must be properly
secured with a forward facing child restraint up to a minimum of forty pounds or the
upper weight limit of the seat.
The changes to the law amend ORS 811.210 and 811.215. These reformations to
the law were created with the safety of Oregon's children as a priority. Questions can
be directed to ACTS Oregon¹s Child Safety Seat Resource Center: ###-###-####,
800-772-1315.
For free reproducible educational material pertaining to the new law visit our
website- http://www.childsafetyseat.org.