Austroads has released fresh findings that redefine how engineers interpret crash data, revealing a stronger link between impact forces and injury risk for vehicle occupants.
The research, backed by full-scale crash testing and supported by Austroads’ recent reports on Predicting Head Injuries from Full-Scale Crash Tests and Standardised Bridge Barrier Design Guidelines, provides a more transparent framework for improving road safety barrier design.
Understanding how physical crash forces correspond to real-world injuries has long been a challenge for designers and regulators. This latest study bridges that gap by comparing the Head Injury Criterion (HIC) and Acceleration Severity Index (ASI), two key measures used in crash tests, with actual injury outcomes observed in testing.
Bridging the gap between data and safety
“Road safety barriers are vital for protecting vehicle occupants, but the industry has recognised the need for better ways to evaluate how barriers perform in real crashes,” says Michael Nieuwesteeg, Austroads’ Road Safety and Design Program Manager.
“This research builds on existing safety rules by providing clear, evidence-based insights into the link between crash forces and injury risk.”
Data analysis from Austroads’ full-scale bridge parapet test showed that stiffer barriers, such as concrete parapets, can generate higher ASI values, an indicator of greater deceleration, which in turn can elevate the probability of head injuries.
The report found that while some barriers meet current standards, they can still pose higher risks for smaller or more vulnerable occupants due to the way forces are distributed during impact.
The correlation between ASI and HIC was confirmed to be exponential rather than linear, indicating that injury severity increases rapidly as crash forces rise. This finding could influence how future safety hardware is assessed and deployed, especially on bridges where barrier stiffness is necessary.
Real-world testing for safer roads
A significant contribution to the research comes from Austroads’ recent full-scale crash test, which assessed a bridge parapet barrier using MASH protocols.
The test involved two anthropomorphic test devices, a 5th percentile female driver and a 1.5-year-old child passenger, in a vehicle travelling at 100 km/h at a 25-degree angle.
The adult dummy registered a strong head impact, likely with the side window, but remained within safe limits for head and chest forces.
The child dummy experienced low forces, showing minimal injury risk.
These results align with broader findings that while barrier stiffness increases ASI, occupant protection can remain within safe thresholds if designs account for occupant variability.
Nieuwesteeg says the research underscores the importance of ongoing refinement.
“It highlights the need to keep improving how we test and interpret data, especially for bridge barriers and other rigid roadside infrastructure,” he says.