(CNN) -- The Obama administration on Wednesday proposed new tests and standards that would for the first time require child safety seats protect occupants from side-impact crashes.
The National Highway Traffic Safety Administration said the rules, which are mandated by Congress and would apply to all car seats for children weighing up to 40 pounds, could save lives.
"We estimate that this proposal would save the lives of five children every single year, and prevent over 60 injuries each year," NHTSA Acting Administrator David Friedman told a Society of Automotive Engineers gathering in Washington.
NHTSA said manufacturers in recent years have begun beefing up car seat structures and adding more padding to protect the head and torso, noting that those products are effective at protecting kids.
But the government wants protocols in place for testing those products as well as formal performance standards for safety in side-impact crashes, which kill or seriously injure as many children as frontal-impact collisions, the agency said.
There currently is a federal safety requirement car seats must meet for frontal crashes.
Traffic fatalities involving young children have dropped sharply since the mid 1970s partly due to increasing use of car seats, NHTSA said.
In data outlined by NHTSA in its proposal, more than 320 children four and younger were killed in all types of passenger vehicle crashes in 2009. Slightly more than half were in car seats.
The new sled tests proposed by NHTSA would simulate a "t-bone" crash in which a small vehicle containing a child seat and traveling at 15 mph is struck broadside by another vehicle going twice that speed.
Manufacturers would have to demonstrate that child seats can safely restrain an occupant and minimize force from the accident that is transmitted to the child's upper body.
Crash-test dummies representing the characteristics of children at ages 1 and 3 will be used.
NHTSA said in its proposal that real-world data indicate head injuries are most common in side-impact crashes.
The public will have 90 days to comment once the rules are published in the Federal Register. Comments, especially by industry, could also result in changes and finalizing a rule could take several months at least.
If new requirements are ultimately put in place, car seat manufacturers will likely have several years to comply with new standards.