The Body
The science of injury. What a crash, a fall, a blast, or a blow does to a person, cited to the medicine, and what that means for proving the case.
Unprotected
What a vehicle does to a person on a bicycle. In 2024, 1,075 bicyclists were killed in crashes with motor vehicles, the third-highest count ever recorded and 73 percent above the 2010 low; the federal count, which is broader, puts the toll at 1,103 killed and about 52,887 injured. Eight in ten died in cities, six in ten away from any intersection, more than half in the dark, and the deaths peak between six and nine in the evening. Pickups, SUVs and vans, the federal light-truck class, were the vehicle most often involved, and in nearly nine of ten of those crashes the rider was struck by the front of the vehicle. In most deaths the worst injuries are to the head. Why a rider sits higher than a person on foot and lands harder, what Texas law gives a bicycle and asks of it, the lamps the code requires after dark, how a rider’s own mistake divides a recovery rather than ending it, and what the record of such a crash contains.
On Foot
On foot: a person struck by a vehicle has no crumple zone, no belt and no steel, and what happens to the body is decided by three things the person did not choose: how fast the vehicle was going, how tall and blunt its front end was, and whether it was dark. The speed curve from the crash data, why a car is more likely to throw an adult onto the hood while a tall pickup or SUV is twice as likely to knock the person down and run over them, the share of these deaths that happen in the dark and away from intersections, and the Texas law that puts due care on the driver even when the person was not in a crosswalk.
Ice on the Wing
Ice on the wing: a wing makes lift by keeping the air attached to it, and ice is the one thing that can take that away without the pilot seeing it happen. What clear ice is and why big supercooled drops make it, why a thin rough layer can cost a wing nearly a third of its maximum lift and moves the stall to a lower angle and a higher speed, why the tail collects ice faster than the wing and cannot be seen from the cockpit, what certification does and does not promise, the other edge of the band where a jet runs out of speed margin, the arithmetic of a descent measured in tens of thousands of feet a minute, and what the record of a flight holds, all in the FAA’s own words. Never a cause.
Distance Lies
Distance lies: a driver waiting to turn left does not see how fast the oncoming car is going. He sees how far away it is, and he turns on that. The seven and a half seconds the guideline gives a left turn, why the same five hundred feet is a safe gap at 35 and a trap at 70, how speed quadruples the energy and nearly triples the stop, why the hit lands on a door with inches to give, what Texas law asks of the turning driver and of the speeding one, and what each number does in a Texas courtroom.
Flashover
Flashover: fire does not spread through a room. For most of its life it stays in the thing that is burning and the room only gets hot; then, in a second or two, everything in the room is burning at once. The gas layer at the ceiling and the temperature that lights the floor, why a modern living room reaches that second in under five minutes and a room of fifty years ago took nearly thirty, the fire that waits behind a closed door for someone to open it, what the federal tests say a smoke alarm buys and which kind, and what each number does in a Texas courtroom.
Threshold
Threshold: a truck does not roll over because it was going fast. It rolls over because, for the load it was carrying, it was going fast enough. The fraction that separates the two, half the track width over the height of the center of gravity, why a car has more than 1 g of it and a loaded van trailer as little as a quarter, the speed-squared arithmetic of a ramp, the 40 percent a soft truck gives away before it tips, why the driver feels nothing until it is over, and what each number does in a Texas courtroom.
Brake Fade
Brake fade: a brake is a machine for turning motion into heat, and on a long grade the hill keeps making more motion than the brakes can turn away. The arithmetic of an 80,000-pound truck on a thousand-foot descent, the temperature at which linings let go and the federal signs built on it, why the engine and not the pedal is the brake on a hill, the one out-of-adjustment brake that dooms the others, how a ramp stops what the brakes could not, and what each number does in a Texas courtroom.
The Air Brake
A loaded truck does not begin to stop when the driver’s foot moves; it begins to stop when the air arrives. The half second of brake lag, the federal stopping-distance standard and the 2009 rule that cut it from 355 feet to 250, the test a truck must pass on the road, what the arithmetic means for the car ahead, why a truck that cannot stop swerves, and what each of those numbers does in a Texas courtroom.
Ride-Down
A crash is a stop, and the only question that matters to the body is how much distance the stop is spread over: a belted person slows with the car across feet of crumpling metal, an unbelted person over inches of dashboard, at several times the force. The arithmetic of ride-down, what the belt and the air bag each do, and the two questions Texas law asks in order.
The Quiet Gas
Carbon monoxide has no color and no smell, and it kills by taking oxygen’s seat in the blood and holding it about two hundred times harder. Why the symptoms look like the flu, why the fingertip monitor reads normal in a poisoned patient, the injury that shows up weeks later, what two Texas storms taught about generators, and what the law asks of the people who sold, rented and ran the machine.
Past the Light
Low beams light about the next two hundred feet, and at highway speed a car needs more than that to stop. How far headlights really reach, the arithmetic of outrunning them, why a dark object appears so late, what the pedestrian count says about the hours after sunset, and how Texas divides a crash at the edge of the beam.
The Egg Carton
A school bus protects children without seat belts by compartmentalization: tall padded seats set close together, so a child thrown forward meets a cushion before he can build speed. Why it works in the crash it was built for, why it fails in a side impact and a rollover, what Texas now requires on every bus, and who answers when a car crosses the line into one.
Low-Side, High-Side
A motorcycle that loses its grip goes down one of two ways: it slides out and falls on its low side, or the tire catches again and throws the rider over the high side. The traction budget, why each fall breaks what it breaks, why the rider could not steer out of it, and what the road keeps as evidence.
Seven Times the Energy
Every car is built for a crash in the thirties: the federal frontal test runs at 35 mph and the toughest side test at 37. A car at 100 carries seven to eight times that energy. The same crash at 40, 50 and 56 mph, how far a car needs to stop, and where speed becomes gross negligence.
High and Heavy
A loaded tanker can roll at a speed that feels ordinary. The fraction that decides when a vehicle tips, what a partly full tank does in a turn, why federal law puts the physics in the driver’s license, and why a tanker that rolls and does not leak is engineering, not luck.
The Splash
A chemical in the eye is the injury where the first seconds decide the most. Acid or alkali, why the water has to be within ten seconds, what the eye doctor looks for, and what the law requires around corrosive chemicals.
The Stand
Deer season starts off the ground. A fifteen-foot fall ends at about twenty-one miles an hour, and in the trauma studies the stand, not the gun, is the hunter’s most dangerous weapon. The physics, the spine, the harness, and the recreational use statute.
The Harness
A fall is decided by the stopping distance, not the height: inches on concrete, three and a half feet in a harness. The physics inside the OSHA fall rule, and whose job it is.
Outweighed
Momentum is shared by weight, so the car takes almost all of the change in speed. Why most people killed in truck crashes were in the other vehicles, and why most truckers who die were in crashes with no other vehicle.
Over the Top
When a motorcyclist goes over a freeway barrier, the wall is not the injury. The fall is. Why the rider separates from the machine, what a body does in the air, and why the height of the drop matters more than the speed of the hit.
The Third Collision
Every crash is three collisions: the car against the object, the body against the car, and the organs against the body. The third one is the one no photograph shows, and it is the one that tears the aorta and shears the brain.
The Roll
Most crashes are one impact. A rollover is a dozen. Why the belt does less in a roll, why the roof and the window are where the injury comes from, and why a tall or loaded vehicle tips when a low one slides.
The Cage
A car in a crash gets a cage built for the purpose. A motorcycle does not, and the rider stands in for it. The biomechanics of a rider against a heavy truck: the crumple zone, the second impact, and the blind spot.
The Reaction
Two cars are closing in the dark and only one nervous system is still working. The pharmacology of impairment behind the wheel: why the sober driver brakes and the impaired driver never does.
The Lucid Interval
He walked away from the wreck and talked to the officer, and two hours later he was dead. The epidural bleed, the middle meningeal artery, and why the calm after a head injury can be the disease.
The Ear
The blast is over in a heartbeat, but the ringing never stops. Why noise and pressure kill the ear’s hair cells for good, why tinnitus and hearing loss are permanent, and why an injury no scan can show is still real.
The Trench
A cubic yard of soil outweighs a small car and a wall of it drops in seconds. How a trench kills, the OSHA rule written in advance, and the gross-negligence door through the comp bar.
The Grade Crossing
A car meeting a train is an aluminum can meeting a car. It cannot stop in under a mile and cannot steer. The physics, and the question of who guarded the crossing.
Current
Electricity burns from the inside out, so the skin lies about the damage, and the heart can fail hours later. How current and arc flash injure, and the law of working the lines.
Crush
A crush injury runs on two clocks, and the second is the deadly one. Traumatic asphyxia, crush syndrome, and why release from the weight can be the fatal moment.
The S-Curve
The neck bends into a shape it was never built to make, and that S, at the facet joints, is where the whiplash injury lives, often with a clean scan.
The Fixed Object
A tree, a pole, a bridge pillar does not move and does not give. Why a car that finds a narrow fixed object is so often the worst wreck of all.
Closing Speed
In a head-on, the two speeds add. Why a median crossover is so much worse than hitting a wall.
Thrown Clear
There is an old belief that being thrown from a car is a kind of luck. The physics say the opposite: the belt and the roof are what save you.
Rhythm
A trauma therapy has you follow a moving finger with your eyes. It often helps. Why it helps is the honest argument.
In the Game
The sense that you can still affect your own recovery is measurable, and the defense will try to use it both ways.
Fertilizer
A fertilizer that feeds a field can level a town. Why an ammonium nitrate blast injures in four ways, and the quiet one that kills.
The Clot
A broken leg can kill a month later, from a clot that formed while it healed. Why stillness is its own injury.
The Wrap and the Ground
A person struck by a car is not hit once. Why the last impact, the ground, is so often the one that kills.
The Second Hit
In a chain-reaction crash, the label hides the one thing that matters: which impact did the harm, and how you prove it.
Inches of Steel
The front of a car has three feet to save you. The door has three inches. Why the turn across traffic is so dangerous.
The Body at 13
A seatbelt was built for an adult body. Why the belt rides onto a child's abdomen, and what submarining does.
Fire
Sometimes the crash is survivable and the fire is not. Why a fuel-fed fire turns a survivable wreck fatal, and the standard meant to stop it.
Wired to Move
Why the hurt person says "I am fine" at the scene and wakes up unable to move. The crash-moment stress response, and the body's own painkillers.
Fog
A concussion can leave the scans clean and the person changed. The brain injury the standard imaging was never built to see.
Controlled Trauma
The surgery that fixes the injury is its own injury. The stress response, and the fog that can follow.
Looking, Not Seeing
Why a driver can stare straight at a parked truck and not see it in time. The perception science.
The Body at 84
The same crash a thirty-year-old walks away from can kill at eighty-four. The biomechanics of age.
Underride
Why hitting the back of a truck at a survivable speed can kill. The physics of the ride-height mismatch.
The Stop
A working muscle is a gland that writes to the brain. Take the movement away, and the mood follows on a schedule.