Interactive Safety Tool

Car Crash Injuries by Speed: What a Collision Does to the Human Body

Choose a collision type and set the impact speed. The figure shows where car crash injuries concentrate on the body; the panel shows the physics behind them. Hover or tap any body zone for detail.

Impact speed
40mph
10City street40Highway80
Injury zones on the body
ModerateSeriousCritical
Hover or tap a body zone for common injuries
0
Peak deceleration on the body
0
Equivalent fall height
0
Braking distance to a stop, dry road
0%
Modeled risk of fatal injury
Crash geometry
Rear end collision
Most common injuries in this crash type
    How to use this tool

    Reading the Visualizer

    The figure above is a map of the human body. When you pick a collision type, the zones most often injured in that crash light up. Gold means moderate injury risk; orange means serious; red means critical. Slide the speed up and watch the colors shift. The same crash that bruises you at 20 mph can break bones at 40 and become life threatening at 60.

    The four numbers under the figure translate the crash into terms you can feel. A 40 mph impact is not an abstract statistic; it is the same energy as falling from a five story building, delivered to your body in about a tenth of a second.

    ZONE COLOR KEY Moderate injury risk Serious injury risk Critical injury risk 10 mph 80 mph
    The science, in plain English

    Why Speed Changes Everything in a Car Crash

    Crash energy does not grow in a straight line with speed. It grows with the square of speed. Double your speed and you quadruple the energy your body has to absorb. That is why the difference between 30 and 45 mph is not “a little worse”; it is more than twice the energy.

    Your body has limits that no amount of caution can change. Bones, organs, and blood vessels can only tolerate so much sudden deceleration, measured in g force. A modern car spends its crumple zones and airbags trying to stretch the crash out over more time and distance, because every extra inch of crush lowers the g load on your body. That is also why side impacts and pedestrian crashes are so dangerous: there is almost nothing between the person and the force.

    The last number in the panel, fatality risk, is the one researchers care about most. For a pedestrian, the risk of death climbs from about 10 percent at 23 mph to about 50 percent at 42 mph. Small speed differences change outcomes dramatically, which is why speed limits near schools and crosswalks are set where they are.

    30 mph 60 mph 4x the energy Impact speed Crash energy
    Collision guide

    The Five Collision Types, Explained

    Rear end collisions

    The most common crash on the road. The struck car is shoved forward while the occupant’s head lags behind for a fraction of a second; the neck absorbs the difference. That is whiplash, and it can occur at speeds as low as 8 mph. At higher speeds, rear end crashes add concussions, spinal injuries, and seat back failures to the picture.

    Head on collisions

    Two vehicles moving toward each other combine their speeds, so a 40 mph head on crash can behave like a much faster impact. The chest takes the belt and airbag load, the head whips forward, and the knees and feet strike the dash and footwell. These crashes produce a large share of serious leg and internal injuries.

    Side impact (T bone) crashes

    A car door offers roughly a foot of protection; the front of a car offers several feet of crumple zone. When a vehicle strikes your door, there is very little structure to absorb the blow. Head, rib, pelvic, and internal organ injuries dominate, and they occur at speeds that would be survivable in a frontal crash.

    Rollovers

    A rollover is not one impact; it is a series of them. Each rotation loads the roof, the occupant’s head, and the spine again. Ejection is the deadliest outcome, and it almost always involves an unbelted occupant. Rollovers make up a small share of crashes but a large share of deaths.

    Pedestrian crashes

    A person on foot has no crumple zone at all. The bumper strikes the legs first, the body rotates onto the hood, and the head reaches the windshield or the pavement. This sequence is why pedestrian injuries cluster in the legs, pelvis, and head, and why fatality risk rises so steeply between 25 and 50 mph.

    Common questions

    Crash Injury Questions, Answered

    Straight answers to the questions people search after a crash. Each one starts with the direct answer, then the research behind it.

    At what speed can a car crash kill you?
    There is no safe speed; fatal crashes have been recorded below 20 mph. For vehicle occupants, the risk of death rises sharply above roughly 40 mph of sudden speed change, and for pedestrians it climbs steeply past 30 mph. Restraints, airbags, and the crash type matter as much as the number on the speedometer.
    Can you get whiplash from a low speed crash?
    Yes. Research shows whiplash injuries can occur in rear end impacts at 8 mph or less, sometimes with little visible damage to either vehicle. Symptoms often appear hours or days after the crash, which is why doctors recommend getting checked even after a minor collision.
    What is the most dangerous type of car crash?
    Per crash, head on collisions and side impacts produce the highest rates of death and serious injury for vehicle occupants, because the closing speed is high or the protective structure is thin. Rollovers are rarer but carry an outsized share of fatalities, largely due to ejection.
    How many g’s can the human body survive?
    A restrained, healthy person can survive brief spikes of 40 to 60 g, and rare cases have survived far more for a few milliseconds. Injury typically begins well below that, though; sustained loads above about 20 to 30 g cause internal damage. Everything in vehicle safety design exists to keep the g number low by stretching the impact over more time.
    Why are side impact crashes so dangerous?
    Because the crumple zone is missing. In a frontal crash your body has several feet of collapsing metal working for it; in a T bone crash it has a door panel. That is why side curtain airbags and reinforced door beams have had such a measurable effect on survival rates.
    What happens to a pedestrian hit at 40 mph?
    At around 40 mph, published research places the risk of death for a struck pedestrian near 50 percent, with typical injuries to the legs, pelvis, and head. At 25 mph that risk is closer to 10 percent. The gap between those two numbers is the entire argument for lower urban speed limits.
    Do seat belts really make that much difference?
    Yes. Federal crash data shows seat belts reduce the risk of death for front seat occupants of cars by about 45 percent, and they are the single biggest factor in surviving a rollover, because they prevent ejection. No other safety device comes close.
    How is the fatality risk in this tool calculated?
    Pedestrian risk is interpolated from published AAA Foundation for Traffic Safety research on impact speed. Occupant risk for the other crash types is a modeled estimate shaped from federal research on sudden speed change and injury. The figures are educational estimates for a typical adult, not predictions for any specific crash or person.
    Transparency

    Methodology and Sources

    Fall height is derived from kinetic energy equivalence. Braking distance assumes a dry road friction coefficient of 0.7 and excludes driver reaction time. Peak deceleration is estimated from typical crush distances for each collision type. Injury zone patterns reflect published trauma literature on collision biomechanics. All figures describe a typical adult and are for education, not prediction.

    Data sources
    For publishers

    Embed or Reference This Tool

    Journalists, educators, and safety organizations are welcome to reference the figures above or embed the tool, free, with attribution and a link back to this page.

    About the publisher

    About J. Alexander Law Firm

    J. Alexander Law Firm, P.C. is a personal injury law firm founded in 2017 by attorney Josh Alexander, a United States Marine Corps veteran who served during Operation Iraqi Freedom. The firm represents people injured in vehicle, workplace, and catastrophic injury cases from offices in Dallas, Fort Worth, Houston, San Antonio, Canton, Oklahoma City, and Tulsa, serving clients in English and Spanish. The firm publishes free public safety tools and guides, including this visualizer, as part of its education and community work.

    Media contact

    Created by J. Alexander Law Firm, a personal injury firm that has spent years studying how crashes injure people. This page is educational and is not legal or medical advice.