The cited stat ultimately comes from
As you surmised, the car stat includes everyone related to cars:
Motor vehicle–traffic includes the following external causes of injury: occupant, motorcyclist, pedal cyclist, pedestrian, other and unspecified person involved in a motor vehicle–traffic incident.
Fortunately, they also break out the numbers for both TBI injuries and deaths by those subcategories:
"Table 10. Average Annual Numbers, Rates, and Percentages of Traumatic Brain Injury-Related Hospitalizations, by Age Group and Specific Motor Vehicle–Traffic (MVT) External Causes, United States, 1995–2001" (subcategories: "MVT—Occupant", "MVT—Motorcycle", "MVT—Pedal Cycle", "MVT—Pedestrian")
MVT-Occupant: average annual rate of 42,000 hospitalizations/injuries ("Note: In-hospital deaths were excluded.")
"Table 15. Average Annual Numbers, Rates, and Percentages of Traumatic Brain Injury-Related Deaths, by Age Group and Specific Motor Vehicle–Traffic (MVT) External Causes, United States, 1995–2001"
MVT-Occupant: 8,819 deaths
They note generally there is underreporting; another paper, after noting that there don't seem to be any decreases in TBI rates post-2001, says that 25% of TBI cases who are knocked unconscious don't seek medical attention, and 14% of those cases seek attention where it wouldn't be recorded in the stats. So that's >42000 injuries and 9k deaths to people inside a car.
Some further reading:
"Traumatic Brain Injury in the United States: An Epidemiologic Overview", Summers et al 2009 https://www.researchgate.net/profile/Karen_Schwab2/publication/24219748_Traumatic_Brain_Injury_in_the_United_States_An_Epidemiologic_Overview/links/09e4150f45b4328311000000.pdf?inViewer=0&pdfJsDownload=0&origin=publication_detail
A Centers for Disease Control and Prevention analysis of hospital, emergency department (ED), and vital statistics databases estimated that about 1.4 million people presented for medical care for a traumatic brain injury (TBI) each year in the United States from 1995 through 2001.^1^ The analysis also found that approximately 50,000 (3.6%) of them died from their injuries, 235,000 (17%) were hospitalized, and 1.1 million (80%) were treated and released from the ED.^1^...A study of data obtained from the 1991 National Health Interview Survey estimated that 25% of individuals with a self-reported TBI that resulted in loss of consciousness did not seek medical attention and that 14% were evaluated in clinics or offices.^3^
...Automobile crashes were the second leading cause of TBI, accounting for an average of 280,000 (20%) cases per year.^1^
...However, more recent research suggests that the incidence of death due to TBI is no longer decreasing at those rates. Rutland-Brown and colleagues10 found that the TBI mortality rate was 18.1/100,000 in 1998 and 17.9/100,000 in 2003. Data from the latest report [2003 or 2006...?] from the Center for Disease Control also indicate that the rate of decrease in TBI hospitalizations has also leveled off.^10^
- National Center for Injury Prevention and Control. Traumatic Brain Injury in the United States: Emergency Department Visits, Hospitalizations, and Deaths. Atlanta, GA: Centers for Disease Control and Prevention; 2006. http://stacks.cdc.gov/view/cdc/13379/cdc_13379_DS1.pdf
- Sosin DM, Sniezek JE, Thurman DJ. "Incidence of mild and moderate brain injury in the United States", 1991. Brain Inj 1996; 10: 47–54.
- Rutland-Brown W, Langlois JA, Thomas KE, Yongli LX. "Incidence of traumatic brain injury in the United States", 2003. J Head Trauma Rehabil 2006; 21: 544–548
OK, so 42k injuries/9k deaths is sobering, but does it justify wearing a driving helmet? I've been curious about this topic and also walking helmets for a while and now that I have my own car again (ironically, given the datasets here, an old 2000 car), the topic of reducing car risks is also of some personal relevance. I'm going to give a stab at a quick and dirty decision analysis here to get an idea of how the case for driving helmets look.
First, we want to convert the absolute numbers to a probability of injury/death per mile driven:
A 2006 study showed that “280,000 people in the U.S. receive a motor vehicle induced traumatic brain injury every year” so you would think that wearing a helmet while driving would be commonplace. Race car drivers wear helmets. But since almost no one wears a helmet while driving a regular car, you probably fear that if you wore one you would look silly, attract the notice of the police for driving while weird, or the attention of another driver who took your safety attire as a challenge. (Car drivers are more likely to hit bicyclists who wear helmets.)
The $30+shipping Crasche hat is designed for people who should wear a helmet but don’t. It looks like a ski cap, but contains concealed lightweight protective material. People who have signed up for cryonics, such as myself, would get an especially high expected benefit from using a driving helmet because we very much want our brains to “survive” even a “fatal” crash. I have been using a Crasche hat for about a week.