This is something I mention in my comments to wreck articles all the time, but for some reason I seem to have forgotten to put it up here. This is a comparison of terminal ballistics between small-arms rounds, and motor vehicles.
First, the dry statistics. according to the CDC a bullet from a small arm like a hunting rifle or a handgun is between 8 and 10% fatal with the majority right in that 9% area of the bell curve. According to the NHWSA and another researcher in the UK who came up with almost the exact same numbers, motor vehicles used against unarmored persons (pedestrians and bicyclists) are 5% fatal at speeds of 20 MPH and below, rising sharply to 50% fatal at 30 MPH, 85% fatal at an impact speed of 40 MPH, over 95% fatal at 50 MPH, and 99+% fatal at speeds of 60 MPH and over. There is always that survivor of a wreck who was hit at 60 or higher speed (like me) that keep the kill ratio under 100%, but for all intents and purposes getting hit at highway speeds is 100% fatal.
Now why that is true is interesting in a gruesome and macabre sort of way. The reason why bullets are so ineffective at killing people even when you actually hit someone with a bullet (which only happens in 1 out of 20 times a trigger is pulled during a firefight where people are actually trying to kill each other) is that bullets are small, and the human body has relatively few places where the would caused by a bullet is fatal, especially once you get away from the head. The head and heart are the only 2 places where a bullet is instantly or very quickly fatal, which is why soldiers are issued torso armor and helmets going into battle. Anywhere else and you die from bleeding to death with the larger the blood vessel compromised the faster you bleed to death. The good thing there is there are few blood vessels that will bleed out so fast that you can’t be saved with quick access to surgery and a blood transfusion. So, bullets, especially in this day and age, are very poor killing devices.
Motor vehicles, on the other hand, despite not actually being designed as killing devices are actually quite good at the job. They kill by massive blunt-force trauma over a large area of the body and sometimes by head injury. As with bullets head and heart injury are quick kills most of the time, and permanent disablers when they don’t actually kill. The difference between bullets and cars is that a bullet hits a single part of the body and creates a very small injury, where a motor vehicle hits large areas of the body and creates large internal injuries and external wounds. A bullet can only compromise a small number of blood vessels, a motor vehicle can remove entire limbs and leave several major blood vessels open to air, or rip major vessels internally causing internal bleeding. Internal bleeding can kill even faster than just dumping the blood on the ground, because the blood then interferes with blood that is still actually getting to its destination by the circulatory system and internal bleeding in the upper chest can cause the heart to stop from the pressure on the organ.
Because of the widespread nature of the injuries administered by a motor vehicle impact, even surviving the initial impact doesn’t mean you’re clear of the reaper yet. There are secondary injuries caused by broken bones piercing vital organs or blood vessels before you get to a hospital or even get in the ambulance. Broken ribs, fractured pelvis taking out major arteries or a heart or lung, or even a broken femur or humerus cutting the major blood vessels in the leg or arm when someone tries to drag a victim off the road so they don’t get hit again. Since you would die if you get hit again this is actually not as bad as it sounds, you have a better chance of surviving not being exposed to another impact.
Now we have body armor that can protect against a bullet penetrating a person to cause injury, what can be done against a motor vehicle? The answer: almost nothing. About the only thing that can protect against a motor vehicle wreck is another, larger motor vehicle or a later model of motor vehicle than the one being used against you, and even that is ineffective in about 28K wrecks a year in the US. Motor vehicles are so deadly that not even a building is sufficient protection against getting killed by one. People inside light wood-frame houses are killed in the dozens every year by motor vehicles crashing through the walls. A bicycle helmet is essentially useless against a motor vehicle wreck. As we have seen even if the head is perfectly protected the massive blunt-force trauma inflicted on the torso by most motor vehicle wrecks will still cause death or permanent injury.
So, what can be done? The only effective technique found so far is to keep motor vehicles and vulnerable users completely separate from each other so they don’t have wrecks. That means Dutch-style infrastructure for bicycles, and protected walking areas for pedestrians, and severe penalties against drivers that hit vulnerable road users. like confiscation of the motor vehicle. It won’t be cheap, and in a few years it will be moot as we run out of gas, but in the mean time we can save lives and protect potential by keeping the murder machines away from their potential victims.