Potential confounding factors were vehicle, occupant, and barrier
related variables including vehicle type, occupant gender, occupant
age, seating position, crash severity, and type of barrier impacted.
Vehicle type was grouped into one of two categories, passenger car
or LTV, based on the“bodytype”variable in NASS/CDS. Seating position was also considered a dichotomous variable: driver or right front
passenger. Occupants were grouped into three categories based on
age: (a) up to and including 24, (b) 25 to 54, or (c) 55 and older.
Equivalent barrier speed (EBS) was used to account for crash severity
with three distinct categories: (a) up to 16 km/hr (10 mph), (b)
16 km/hr to 40 km/hr, and (c) greater than 40 km/hr (25 mph).