Factors Associated with Severe Head Injury in Far-Side Lateral Collisions: Analysis of a National Crash Database

Occupants involved in far-side lateral collisions are at a similar risk of sustaining severe head injuries to those involved in near-side impacts. Previous studies have evaluated injury mechanisms and risk factors using large-scale crash datasets. However, continuous evaluation using more recent vehicle models is necessary to further improve occupant protection. The purpose of the current study was to identify the factors independently associated with severe head injury (Abbreviated Injury Scale [AIS] score ≥ 3) in far-side lateral collisions using the Crash Investigation Sampling System database. We included occupants with head injuries (AIS ≥ 1) involved in far-side collisions between 2017 and 2022. Eligible occupants were seated in the front-left or rear-left (second row) positions and were struck from the right side. Occupants with height < 140 cm were excluded. A total of 107 occupants were analyzed, including 90 with head AIS scores of 1–2 and 17 with head AIS scores ≥ 3. The total change in vehicle velocity and the degree of vehicle intrusion were significantly higher in occupants with severe head injury. No significant differences were observed in seatbelt use, belt pretensioner activation or airbag deployment between the two groups. In multivariable logistic regression analysis, the total change in vehicle velocity was independently associated with severe head injury, whereas seatbelt use, belt pretensioner activation and airbag deployment were not associated with reduced risk of severe head injury in far-side collisions. These findings provide real-world evidence that reducing vehicle velocity prior to impact remains essential for preventing severe head injury in far-side collisions, even in contemporary vehicles equipped with advanced occupant restraint systems.