North Carolina ? U.S. Secretary of Transportation Mary Peters proposed new rules Monday to improve the safety of school bus seats and expand the use of shoulder belts, but declined to order that all new buses include seat belts.

Peters rode a packed school bus to Morrisville Elementary School, among the first schools in the country to equip some of its new buses with seat belts, then said she wants to increase the height of seat backs on all school buses from 20 inches to 24 inches to help protect children during accidents.

Peters also proposed a new requirement for short school buses – the style more prone to rollover accidents – to begin using shoulder straps. For longer buses, however, she instead proposed allowing states the option of using federal highway safety funds to purchase new buses with seat belts.

Statistics from the National Highway Traffic Safety Administration show an average of seven school-age children nationwide die in school bus crashes each year. In contrast, an average of 19 children are killed each year getting on and off the school bus, most of those killed by a passing vehicle or by the school bus itself.