To consider injury trends and to establish bases for potential future risk analyses, we categorized head injuries in real-world frontal crashes as being "brain-related," "bone-related," and/or "otherwiserelated." Specifically, we studied adult drivers in towaway, 11-1 o'clock, full-engagement frontal crashes in the National Automotive Sampling System (NASS, 1995-2012 calendar years, 1985-2012 model-year light passenger vehicles). Those data were considered subject to three levels injury (AIS1+, AIS2+, AIS3+) , two levels of restraint (properly-belted, unbelted), and two eras of technology, based on driverairbag fitment (Older Vehicles, Newer Vehicles). For each injury level, 88 possible bins of data were formed to quantify injury rates for the various head-injury categories, eras, restraint levels, speed changes, and crash severities. The following trends were noted: (a) Over 84% of head-injury cases involved only one of the three head-injury categories, (b) IRAIS3+ < IRAIS2+ < IRAIS1+ , (c) IRbelted < IRunbelted , and (d) IRNewerVehicles < IROlderVehicles. It was also noted that (a) while overall head injury rates have reduced in Newer Vehicles (versus Older Vehicles), those reduced rates have become more brain-related; Older Vehicles had more bone-related contributions, and (b) otherwise-related head injury was primary to the AIS1+ injury studies, but it was tertiary to the AIS2+ and AIS3+ studies.