Recently, we analyzed the results of NHTSA crash tests for 44 vehicles and concluded that the introduction of a driver airbag, even a first-generation one, provided a significant safety improvement. But what about the more controversial passenger airbag? How much of a difference did it make, especially in the early days of its introduction?
This analysis specifically focused on 34 vehicle models tested by NHTSA both with and without passenger airbags. Like the driver airbag evaluation, only models that were structurally unchanged between versions were included—ensuring a fair comparison of safety outcomes.
Early Passenger Airbags: A Modest Safety Boost
As it turns out, first-generation passenger airbags were less effective than their driver-side counterparts in reducing injury risks. On average, the severe injury risk for passengers dropped from 22% to 19% with the inclusion of the passenger airbag—a mere 3% decrease. In comparison, the driver airbag reduced injury risk by 12%. In relative terms, this modest improvement—14%—is a far cry from the 40% reduction seen for drivers with airbags.
A Mixed Bag of Results
Out of the 34 vehicles tested, 20 saw a reduction in severe injury risk, while 14 experienced an increase. Only one vehicle saw an improvement of more than 20%, and nine showed improvements between 10% and 19%. On the other hand, five vehicles experienced a worsening of at least 10%, although none of these changes reached a 20% increase in risk.
Without a passenger airbag, 31 of the 34 vehicles “passed” the test by earning a minimum of 3 stars out of 5 for passenger safety. With the airbag, 33 of the 34 vehicles passed. However, when looking at the highest ratings (4 or 5 stars), 17 models earned this without the airbag, while 21 achieved it with the airbag. Interestingly, fewer vehicles achieved the highest 5-star rating with a passenger airbag than without.
Limited Improvements in Passenger Cars
As with the driver airbags, the safety improvements were more notable in trucks, vans, and SUVs compared to passenger cars. In passenger cars, the average severe injury risk only slightly increased, from 17% to 19%. However, due to the small sample size (16 models), this change is not statistically significant and can be considered a plateau in safety. Of these vehicles, 7 showed improvement, while 9 saw worsening results.
For trucks, vans, and SUVs, there was a more noticeable improvement, with the average severe injury risk decreasing from 26% to 18%. Of these, 13 vehicles improved, and 5 showed worse results.
Head Injury Reduction with a Trade-Off
As with driver airbags, the safety benefits of passenger airbags were largely focused on head injury risk reduction. The Head Injury Criterion (HIC) dropped from an average of 808 to 603, a 25% decrease. However, chest injury risks, measured by “chest G’s,” increased from 48.1 to 52.0, an 8% rise. This suggests a trade-off: a significant decrease in head injury risk at the expense of a slight increase in upper body injury risk, resulting in a moderate overall reduction in injury risk.
For passenger cars, the average HIC dropped from 741 to 637 (a 14% decrease), while chest G’s rose from 44.9 to 51.1 (a 14% increase). In trucks, vans, and SUVs, HIC dropped from 868 to 572 (a 34% reduction), while chest G’s increased slightly from 51.0 to 52.8 (a 4% rise), indicating a negligible impact on chest injury risk.
Why Were Passenger Airbags Less Effective?
The limited performance of early passenger airbags can be explained by basic physics. Passengers sit further away from the dashboard (20-24 inches) compared to drivers (11-13 inches), which means that a seatbelt alone can often prevent severe head contact in a crash. Many early passenger airbags were too aggressive or inflated too firmly, and in certain crashes, they offered no added benefit over the seatbelt alone.
Interestingly, the trucks, vans, and SUVs tested were, on average, two years newer than passenger cars. These vehicles often received airbags later, and as airbag designs evolved to become less aggressive, these vehicles tended to perform better in safety tests.
Is a Passenger Airbag Worth It?
While the early models of passenger airbags did not provide dramatic safety improvements, they were still beneficial, especially in preventing head injuries. However, for many cars, the seatbelt alone could offer significant protection during frontal crashes. Nevertheless, passenger airbags have come a long way over the years, especially with the introduction of depowered airbags in 1998, which reduced the risks posed to passengers while still providing enhanced protection.
Conclusion: Passenger Airbags Have Evolved
Despite their rough start, passenger airbags have significantly improved in the past three decades, especially as car manufacturers refined the technology. By fine-tuning airbag designs and integrating them with improved seatbelt systems, automakers have enhanced passenger safety to levels that would have been impossible without airbags.
Today, passenger airbags are a crucial component of modern vehicle safety systems, and they continue to evolve as technology improves. Though early models were somewhat limited in their effectiveness, the ongoing progress in airbag design shows just how far this life-saving technology has come, helping reduce injuries and save lives on the road.
