Most people in a serious car crash walk away without any head injury, and when one does happen it is usually a concussion rather than a skull fracture or a brain bleed. Still, head injuries cause a large share of crash deaths, so the rare severe cases matter a great deal. Who gets hurt depends less on luck than on things that can be predicted: how people are buckled in, how old they are, which way the car is hit, and what it collides with.
How Often Car Crashes Cause Head Injuries
A concussion is a brain injury caused by a jolt that temporarily disturbs how the brain works. It often brings headache, confusion or gaps in memory. In crashes serious enough that a car must be towed, about 1.6 to 1.7 in 100 occupants get one.1PubMed Central. Head injuries (TBI) to adults and children in motor vehicle crashes In the US, that adds up to tens of thousands of concussions a year among crash occupants.2PubMed. Concussion, Diffuse Axonal Injury, and AIS4+ Head Injury in Motor Vehicle Crashes
Common signs are headache, feeling dazed or foggy, dizziness, trouble concentrating, and sensitivity to light or noise. Many people never lose consciousness, so being awake the whole time doesn’t rule a concussion out. Some can’t remember the crash or the minutes around it, and that memory gap is itself a sign the brain was affected. Neck pain and headache overlap after a crash, which makes it hard to tell for yourself which one is causing the trouble. It is also easy to miss one at the scene. Adrenaline can mask headache and confusion for hours, and nausea, sleepiness or irritability may only show up later that day or the next. Anyone with these signs after a crash should get checked, even if they felt fine at first.
A concussion can also happen without any blow to the head. The brain can be injured when the head is whipped forward and back or sideways, even if it never touches anything. Seatbelts and airbags can still leave the head moving violently, so a person with no bump, bruise or cut may still have one.
Severe, life-threatening head injuries are much rarer, affecting roughly 0.3 to 0.4 in 100 tow-away crash occupants.3PubMed. Concussion, Diffuse Axonal Injury, and AIS4+ Head Injury in Motor Vehicle Crashes Skull fractures affect about 0.2 to 0.3 in 100.4PubMed Central. Head injuries (TBI) to adults and children in motor vehicle crashes Yet head injury is the direct cause of over 7,000 US crash-occupant deaths a year.5PubMed Central. Head injuries (TBI) to adults and children in motor vehicle crashes6PubMed. Incidence and risk factors of severe traumatic brain injury resulting from road accidents: a population-based study7PubMed. The incidence of brain trauma caused by road injuries: Results from the Global Burden of Disease Study 2019
Most Crash Head Injuries Are Mild, but Not All
Doctors rate brain injury with the Glasgow Coma Scale (GCS), a score from 3 to 15 based on eye opening, speech and movement. A score of 13 to 15 is mild and 8 or below is severe. A person who is alert, talking normally and following commands scores 15. The score is usually taken on arrival and can be repeated, and a falling score over hours is a worrying sign.
Among crash patients with brain injury at one emergency department, 81% were mild, 3% moderate and 16% severe.8Orthopedic Reviews. Motor Vehicle Collision Associated TBI: Predictors of Injury severity People who had to be cut out of their vehicle were about three times as likely to have a severe coma scale score, 12% versus 4%.9PubMed Central. Extrication as a Predictor of Outcome in Motor Vehicle Crashes
Sudden spinning and stopping of the head stretches brain tissue, and faster, longer rotation causes more strain.10PubMed Central. Head Rotational Acceleration Characteristics Influence Behavioral and Diffusion Tensor Imaging Outcomes Following Concussion In high-speed crashes, nerve fibers deep inside the brain can tear in specific regions, a damage pattern typical of road crashes.11PubMed. Current concepts: diffuse axonal injury-associated traumatic brain injury This deep tearing is rare, affecting about 0.05 in 100 tow-away occupants.12PubMed. Concussion, Diffuse Axonal Injury, and AIS4+ Head Injury in Motor Vehicle Crashes
Seatbelts, Airbags and Crash Direction
Being unbelted is one of the strongest factors linked to brain injury in crashes.13PubMed. Preventive effects of seat belts on traumatic brain injury in motor vehicle collisions classified by crash severities and collision directions Airbags, alone or with seatbelts, lower the risk of head, face and spine injuries.14PubMed Central. Seatbelt versus seatbelt and airbag injuries in a single motor vehicle crash The belt holds the body in place so it doesn’t hit the dashboard, wheel or windshield, and keeps the person positioned for the airbag. The airbag then cushions the head and chest once the belt starts to restrain. An unbelted person can be thrown at an inflating airbag from the wrong position, which is why an airbag alone is weaker protection.
Belts protect best within certain crash severities, so they cut risk but don’t erase it in the worst crashes.15PubMed. Preventive effects of seat belts on traumatic brain injury in motor vehicle collisions classified by crash severities and collision directions Some common mistakes weaken them. A shoulder belt tucked behind the back or under the arm removes upper-body restraint, and the lap belt should sit low across the hips, not the stomach. Adults in the back seat are often unbelted, yet they face the same forces.
Side impacts are linked to more brain injury than other crash types.16PubMed. Preventive effects of seat belts on traumatic brain injury in motor vehicle collisions classified by crash severities and collision directions There is only a door’s width between the occupant and the striking vehicle, and the head can hit the window, the pillar or the other car directly. Side curtain airbags exist to fill that gap. For children, rollovers carried about 8.6 times the head injury odds of frontal crashes, and side impacts on the child’s side about 2.4 times.17PubMed. Factors associated with clinically significant head injury in children involved in motor vehicle crashes
In a rollover, the head can strike the roof, side windows and pillars several times from different directions. An unbelted occupant can be thrown around the cabin or partly or fully out of the vehicle, which greatly raises the risk of severe injury. Rollovers that also involve hitting something were more often fatal than simple rollovers.18PubMed Central. Planar impacts in rollover crashes: significance, distribution and injury epidemiology
Seat position matters too. Riding with the seat fully reclined lets the body slide under the belt and increases the head’s forward jolt in a frontal crash.19PubMed Central. Influence of a Passenger Position Seating on Recline Seat on a Head Injury during a Frontal Crash Keep the seatback upright while the car is moving.
Children and Car Seats
Only about 15% of unrestrained infants escaped head injury in a crash, versus about 93% of properly restrained infants.20PubMed. Risk of pediatric head injury after motor vehicle accidents Moderate-to-severe head injury fell from 7% to 0.5% in infants with a properly used seat.21PubMed. Risk of pediatric head injury after motor vehicle accidents The protective gap is smallest in teenagers, who are often belted loosely or not at all.22PubMed. Risk of pediatric head injury after motor vehicle accidents
Unrestrained children had about three times the odds of head injury.23PubMed. Factors associated with clinically significant head injury in children involved in motor vehicle crashes Children riding with drivers under 25 had about 1.4 times the odds.24PubMed. Factors associated with clinically significant head injury in children involved in motor vehicle crashes
“Properly used” starts with a seat matched to the child’s age and weight. Infants and toddlers ride rear-facing, where the seat shell supports the head, neck and back and spreads crash forces across the whole body, and they should stay that way as long as the seat allows. Children who outgrow the rear-facing limits move to a forward-facing seat with a harness, then to a booster that positions the adult belt correctly. A child moves up only after reaching the limits of the current seat, since each step gives somewhat less protection than the one before.
To check the harness, buckle the child in and try to pinch the strap at the shoulder. If you can pinch a fold of webbing, tighten until the strap lies flat. The chest clip belongs at armpit level, because a clip too low can let the straps slip off the shoulders. Bulky winter coats compress in a crash and leave slack, so put a thin layer under the harness and a coat or blanket over it. Free inspection checks at fire stations or with certified technicians can catch installation errors.
Why Older Adults Face Greater Danger
Deaths from crash head injury rise from about age 60, even when crashes are less severe and injury scores are similar.25PubMed. Age: is it all in the head? Factors influencing mortality in elderly patients with head injuries Older occupants more often hit the airbag, door or seat.26PubMed. Age: is it all in the head? Factors influencing mortality in elderly patients with head injuries Belted older occupants had about 10 times the risk of bleeding on the brain’s surface (a subdural bleed) in frontal crashes and 8 times in side crashes, compared with younger belted occupants.27PubMed. Accident analysis to support the development of strategies for the prevention of brain injuries in car crashes
The reason lies partly in the brain itself. With age the brain shrinks slightly, leaving more room between it and the skull. The small veins that bridge this space become stretched and fragile, so a sudden jolt can tear them and cause bleeding between the brain and its outer covering.
Older bodies also tolerate impact forces less well, so a crash a younger person walks away from can cause serious injury. Frailty, existing health conditions and slower recovery make complications more likely and healing harder.
These bleeds can grow slowly over hours or days, so an older relative who seems fine after a crash still needs watching. New confusion, a worsening headache, drowsiness or weakness are the signs to look for. Blood thinners raise bleeding risk, so tell doctors about them right away. For protection, older riders should sit upright and well back from the airbag, and vehicles with side curtain airbags help.
Vehicle Size, Alcohol and Other Risk Factors
A lighter vehicle is generally at a disadvantage against a heavier one.28IIHS-HLDI crash testing and highway safety. Vehicle size and weight Taller SUVs and pickups, especially older ones, can ride over a small car’s hood, raising injury risk for its occupants.29IIHS-HLDI crash testing and highway safety. Vehicle size and weight The lighter vehicle absorbs more of the change in speed, so its occupants feel stronger forces. A tall front end can strike a small car above its strongest structures, near the doors and windows and close to the occupants’ heads.
When choosing a vehicle, check crash ratings from IIHS or NHTSA before buying. Newer SUVs have lower energy-absorbing structures that align better with cars, and within a class, heavier vehicles generally protect occupants better.
After accounting for speed, belts and vehicle damage, drinking drivers were more likely to be seriously injured or killed in a given crash.30PubMed. The potentiating effects of alcohol on driver injury Crash victims with alcohol in their blood were about twice as likely to have a worse brain injury on CT scan.31PubMed. The effects of alcohol on head injury in the motor vehicle crash victim Drinkers are more often unbelted and in faster crashes, but the risk stayed higher even after accounting for that. One trauma-center study did find heavily intoxicated patients had fewer severe head injuries, so the evidence is not fully consistent.32PubMed Central. Is Blood Alcohol Level a Good Predictor for Injury Severity Outcomes in Motor Vehicle Crash Victims? Overall, the belief that being drunk protects you in a crash is not supported.33PubMed. The potentiating effects of alcohol on driver injury Women face higher injury risk than men in identical crashes, partly because safety systems were designed around male bodies.34IRCOBI Conference. Assessment of Male and Female Responses in Frontal Crashes with Focus on Occupant Protection, Neck Responses and Cervical Facet Angles
Safety Technology That Lowers Head Injury Risk
In crash simulations, automatic emergency braking cut concussion risk in a severe frontal crash from about 71% to 31%.35Frontiers in Future Transportation. Effects of Automated Emergency Braking and Seatbelt Pre-Pretensioning on Occupant Injury Risks in High-Severity Frontal Crashes Cameras or radar watch the road ahead and measure how quickly the car is closing on something. If the driver doesn’t react in time, the system first warns and then brakes by itself. These systems work best at lower and moderate speeds and may not stop the car in every situation, so they supplement attentive driving.
Even small speed reductions lower head impact speed.36International Journal of Crashworthiness. Potential head injury mitigation of M-AEB in real-world motorcycle crashes Crash energy grows faster than speed does, so a modest drop cuts the energy the body and brain must absorb by a larger share. Braking even a fraction of a second before impact can turn a severe crash into a moderate one, which is why automatic braking helps even when it can’t prevent the crash.
For pedestrians, combining emergency braking with softer hood designs prevented far more severe head injuries than either alone.37Safety Science. Integrated pedestrian countermeasures – Potential of head injury reduction combining passive and active countermeasures Padding the upper interior of the cabin can also reduce head impact severity.38Monash University Accident Research Centre. Prevention of head injuries to car occupants: an investigation of interior padding options
Automatic emergency braking is now standard on most new cars. Side curtain airbags protect heads in side crashes and rollovers.
What Happens After a Serious Head Injury
About 27% of people with serious brain injury in one population needed emergency brain procedures, most often a pressure monitor or removal of a blood clot.39PubMed Central. Incidence of emergency neurosurgical TBI procedures: a population-based study A pressure monitor is a small sensor placed through the skull to measure pressure inside the head, which can rise dangerously after injury. Removing a clot means opening part of the skull to relieve pressure on the brain. Both are meant to protect brain tissue from further damage.
Up to 65% of people with moderate or severe brain injury report lasting thinking problems.40PubMed Central. Cognitive Sequelae of Traumatic Brain Injury About 43% have disability lasting six months or more,41PubMed Central. Cognitive Sequelae of Traumatic Brain Injury and nearly a quarter don’t return to work within a year.42PubMed Central. Cognitive Sequelae of Traumatic Brain Injury Crash victims often have other injuries, like spinal, facial or limb damage, that add to disability.43PubMed Central. Chronic impact of traumatic brain injury on outcome and quality of life: a narrative review In one Canadian province, crash brain injuries cost about $161 million in lifetime costs from a single year, mostly lost work.44Canadian Journal of Neurological Sciences. Health & Economic Burden of Traumatic Brain Injury in the Emergency Department
Recovery is usually fastest in the first months, as swelling falls and the brain adapts. Progress then slows but can continue for a long time, so a slowdown doesn’t mean recovery has stopped. Rehabilitation usually starts early and may include physical, speech and occupational therapy. Memory, attention and mood changes are common and worth reporting.
Most concussions improve within weeks. Symptoms lasting beyond a few weeks deserve a follow-up visit, and it helps to ease back into work, screens and driving gradually.