(Read more: Youth sports is a $7 billion industry—and growing)
NHTSA estimates that the proposal would save five lives and prevent 64 injuries annually.
The proposal has been under consideration for a decade and child seat makers have been introducing models marketed to protect children in side crashes. Safety 1st, for example, sells two models—the Advance 70 Air Convertible Car Seat and the Elite 80 3 in 1 Car Seat—which both provide full body side impact protection.
"In 2003, when this rule-making began, we knew that kids were being hurt in side-impacts, but we didn't know what the mechanisms of injury were," child safety advocate Joseph Colella said Wednesday. "Developing appropriate test devices and configurations could not begin until that was better assessed."
More from USA TODAY:
Are you sitting down? Your heart failure risk is higher
Fewer women seek help for infertility, data show
Airports add outlets to serve power-parched passengers
A federal rule would help assure consumers that all seats sold meet a minimum level of safety in side crashes.
"Today's proposal will give parents and car seat makers important new data on how car seats perform in side crashes," said Transportation Secretary Anthony Foxx.
Under the proposal, car seats would be tested in a specially-designed sled test that simulates a "T-bone" crash, where the front of a vehicle traveling 30 mph strikes the side of a small passenger vehicle traveling at 15 mph.
(Read more: What's it cost to have a baby? Try $3000—or $37000)
This test is the first of its kind in the world being proposed for regulation. It simulates both the acceleration of the struck vehicle and the vehicle door crushing toward the car seat. Along with using an existing 12-month-old child dummy, the proposed test will also utilize a planned side impact dummy representing a 3-year-old child. The agency proposed a 3-year timeframe for car seat manufacturers to make any necessary changes to meet the proposed requirements upon final rule publication.
This year will be a big one when it comes to federal rulemaking on child seats.
NHTSA is also expected to issue a final rule very soon on the child-seat attachment system known as LATCH for Lower Anchors and Tethers for Children. Comments on the rule close Wednesday. The rule is expected to go into effect by late next month.
Parents are expected to be advised to use seatbelts—instead of LATCH—to secure car seats if the child and seat weigh more than a certain amount, likely 65 pounds combined. The agency may require car seat manufacturers to place a label, which would go on the car seat, specifying the maximum weight a child can be secured using LATCH.
For example a car seat weighing 25 pounds would need a label that says, "LATCH may only be used for children weighing 40 pounds or less." This is to ensure LATCH can withstand the forces from all types of collisions, NHTSA says.