The tragedy on a New Jersey highway in May involving a school bus and a dump truck horrified the nation while also raising familiar questions about school bus safety. The impact ripped the body of the bus off its chassis, killing two people and injuring most of the 45 passengers on board. By one witness’s account, “A lot of people were screaming, and they were, like, hanging by their seat belts.”

The sobering image of terrified children suspended by seat belts begs an important question – might the number of fatalities have been higher if New Jersey did not mandate seat belts on school buses?

Currently, eight states have a school bus seat belt law — New Jersey, California, Florida, Louisiana, New York, Texas, Nevada and Arkansas. Although similar legislation has been introduced in other states, opponents of such proposals argue statistics on school bus safety show that, even without seat belts, students are safer taking the bus than driving to school with their parents.

In addition to bright yellow paint and flashing lights, school buses are designed with a passive protection system called compartmentalization. This technology utilizes high, padded seats constructed with materials that absorb energy from an impact, protecting students “much like eggs in a carton.”

But even eggs in a carton will break when exposed to excessive force.

Investigations reveal that compartmentalization works well for front and rear end crashes but is less effective in protecting children from side impact or high-speed rollover collisions. For this reason, the National Transportation Safety Board recommends that new buses be equipped with three-point seat belts.

The NTSB had its first ever glimpse of seat belts in action when a bus equipped with three-point seat belts slid off a road in Anaheim, California in 2014. Although the driver and nine passengers were injured when the bus collided with a light post and multiple trees, there were no fatalities. Video monitoring inside the bus revealed that, despite the significant forces flailing belted students about, they remained restrained within their seats. Simulations compared this outcome with the same students if they had been secured with only lap belts and if they wore no belts at all. Lap-belted occupants were found to be susceptible to upper body injury. Unbelted occupants would have been hurled toward the side of the bus impacting a tree, and, even worse, the simulations predicted these students would have been either partially or fully ejected.

Crash data from personal vehicles support the NTSB’s findings. Unrestrained occupants are thirty times more likely to be ejected from a vehicle, and over three-quarter of people ejected in a fatal car collision will die.

One of Newton’s laws of motion tells us that the force of an object is equal to its mass times its acceleration. Unrestrained children are at increased risk of becoming projectiles when exposed to the higher forces resulting from greater speeds. The proper use of seat belts in cars has significantly diminished the possibility of ejection in private vehicles while making a notable impact in reducing overall mortality from car crashes. The undeniable fact is that most car crash deaths in occur when occupants are unrestrained.

The additional cost of equipping buses with seat belts is estimated at $7,000 to $10,000 dollars per bus — a staggering figure for most financially strapped school systems. Coupled with the low average rate of six school bus passenger deaths per year, investing in seat belts for all school buses is understandably a hard sell.

But when a serious school bus accident does happen, we should not be left wondering if everyday technology like seat belts could have saved lives. All available data show that three-point seat belts in all buses are the safest option for our children. A seat belt requirement for school buses that use roads with higher speed limits is a less optimal though perhaps more economical approach. Such investments ensure our children are truly handled with care.

Aida Cerundolo is an emergency physician.

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