A better way to put this situation is that it’s not how fast you are going as much as how fast are you stopping. The human body can only take so much deceleration before it ends up injured. In an accident there are at least three collisions that occur. The first is the vehicle (or as Newton would say – the object in motion) decelerating as it impacts another object. The other is your body being slowed down by such things as belts, air bags, and portions of the vehicle’s interior. Finally all the soft tissues inside your skin (and skull) also being subjected to rapid deceleration. Just ask Richard Hammond, of Top Gear fame, who survived a rollover crash in a jet car traveling 288 miles per hour.
Today’s vehicles are designed with a sort of encapsulated frame designed to isolate the passenger area from most of the crushing effects of a collision. Known as crumple zones they are areas of the vehicle that are intended to sacrifice their integrity so that as much energy as possible is expended by the time the passenger compartment is directly involved with a collision. Front engines are designed to slide under the passenger compartment and fenders and trunks are designed to collapse all in the name of absorbing energy that would otherwise be transferred to the passenger compartment and the vehicle’s occupants.
Of course you can be traveling at great speed, lose it on a corner, spin off the road, slide across a grassy area, and come to a stop. Again, the speed doesn’t kill unless you collide with something.
Walk into a wall and you will bruise your head. Do the same on a skate board and I hope you are wearing a helmet. Restrain your body in a car and hit a wall and you could find out what Dale Earnhardt did when his NASCAR ride hit the wall at one o’clock. Your body will be restrained, but your head is not and will be compelled to keep going unless you have an air bag or HANS device to save you.
Avoid rollovers. The national average is that a third of vehicle deaths are due to rollovers. That is just the national average, in Montana it is twice that as indicated in the excerpt from the NHTSA’s report titled: An Analysis of Motor Vehicle Rollover Crashes and Injury Outcomes
“In 2004, for the United States as a whole, 31,693 passenger vehicle occupants were fatally injured in crashes of all types, 10,553 were fatally injured in rollovers, and 8,565 were fatally injured in single-vehicle rollovers. This means that 33% of passenger vehicle occupant fatalities were in vehicles that rolled over. State-by-State, this percentage ranged from 10% for the District of Columbia to 67% for Montana.“
If you are going to be in a rollover it pays to be short and light. Here is another conclusion from the same report:
“One finding of this section is that among fatally injured drivers, those who were restrained tended to weigh more, be taller, and have a higher BMI than those who were unrestrained. Another interesting finding is that drivers who weighed less, were taller, and had a lower BMI tended to be overrepresented in single-vehicle fatal rollovers. Thus, while heavier individuals received fewer benefits from seat belts, they might also have been at a lower risk of fatality given involvement in a single-vehicle rollover. On the other hand, this over representation of lighter, taller, and lower BMI drivers could be related to age and its relationship to risk-taking.”
Do I need to add that seat belt usage improved the odds? Here is a quote from another NHTSA report entitled: Characteristics of Crash Injuries Among Young, Middle Age, and Older Drivers
“There was a statistically significant reduction in injury severity in both rollover and non-rollover crashes to the driver when seat belts were used. Non-belted drivers were eight times more likely than belted drivers to sustain serious injury. The driver serious injury risk (odds) in vehicle rollover crashes is three times higher than that in vehicle non-rollover crashes.”
Pay attention to the emphasis on fatalities. These figures don’t include the percentage of incapacitating injuries that occur at a higher rate.
As you may have noticed the weight of vehicles in each class has been rising over the years. For example, you could have bought a Ford Fiesta in 1978 that weighed in at just over 1800 pounds while today your Ford Focus would weigh in at about 2600 pounds. Some of this could be attributed to additional features and a bit more luxury, but the vast amount of extra pounds have been to design in crash worthiness into the vehicles.
Do you need another example? Noel provided a link to this news article from the Saratogian where rescue workers comment on how much more difficult it is becoming to extricate occupants from a vehicle that has been involved in a collision. Where is used to take ten to fifteen minutes of use of hydraulic cutters, saws, and metal benders, it can now take twice as long. The crews also have to be aware of just what they are cutting through and not set off airbags. Hybrid cars introduce additional concerns of hidden power cables. All these delays impact the “golden hour” or the period of time where critically injured people have the highest chance of survival if they can be extricated and moved to a hospital.
Don’t get me wrong, I like safety features. I wouldn’t drive without using at least a three point safety belt. I wouldn’t drive in an autocross or track day event without a helmet. I am glad that car designs include crumple zones and reinforced passenger compartments. Just keep in mind that there is no free lunch here. What has been done to minimize your injury potential may impact just how quickly you can be rescued.
Does speed kill? Stopping too fast (say a 40G impact) can definitely kill. If we take it to its extreme we could insist that all vehicles travel a zero miles and hour and therefore eliminate all accidents. Unfortunately we would also eliminate all the benefits of transportation of food, materials, people, etc. There are risks in everything. It is the circumstances that put you in that situation that can kill. Doing things that keep us from focusing on the job of driving provide far more risk than the speed at which we travel. Getting proper training on vehicle dynamics and handling limitations is not a bad idea either.