Garth Rattray | Death in milliseconds

Despite the annual carnage on our roads, many drivers are not considering the innumerable ways that they are endangering themselves and other road users.

Widely posting macabre images and videos of mangled motor vehicles along with contorted, dying and dead human bodies on social media has done nothing to stem the stupidity on our roads. Mainstream media broadcasting the lamentations and wailing of mourning family members, relatives, friends and acquaintances has not tamed the road hogs. Pleading to and prosecuting bad drivers have not positively influenced the air heads and heavy feet of selfish and aggressive drivers who are intoxicated by the power of the machines that are under their control.

Crashes occur in four dimensions. The fourth dimension is time. When traffic crashes occur, and the speed at which they occur, are extremely important. Additionally, when a crash occurs, things happen in milliseconds, one thousandth of a second. I believe that, if people had a little understanding of the science (physics) behind motor vehicle crashes (impacts), it would help them to think about what they do on our roads.

Many people do not realise that crashing head on, which often occurs with improper overtaking, results in adding the speeds of the vehicles together.

If each vehicle crashes head on into the other when each is [only] travelling at 50 km/h, each vehicle will experience an impact which is equivalent to crashing directly into an immovable concrete wall at 100 km/h. That’s like falling from a height of approximately 39.3 metres, which is the same as falling from the 13th floor of a building. Such an impact, at that relatively low [individual] rate of speed, is extremely serious.

You will understand that, even if the impact occurs at a right angle, which is obviously not head on, the ‘T-bone’ (side-impact) crash will still result in significant damage and possible fatality. The only real saving grace in any crash is the speed of the vehicles involved. The primary and secondary safety devices and features can only do so much and no more to protect you and others.

To that end, it has been [scientifically] determined that, the optimal maximum [urban] speed for convenience and safety is 30 km/h. At this speed, the risk to motor vehicles, pedestrians, and cyclists is minimised. Studies of pedestrian survival rates show a 90 percent survival rate if struck by a vehicle travelling at 30 km/h but falls below 50 percent survival rate if struck by a vehicle travelling at 50 km/h. There is a 2-fold increase in fatality between 30 and 40 km/h, and a six-fold increase in fatality between 30 and 50 km/h.

Additionally, a speed of 30 km/h allows for a better reaction time to avoid hazards and evade the object or come to a complete stop. International transport forums put out that infrastructures should be designed to ensure that impact speeds will be below 30 km/h to prevent fatalities when human errors occur.

Taking into account safety, fuel efficiency, traffic flow, road surface, environmental conditions (rain, fog, luminance), and terrain, the optimal highway speed for safety is between 80 km/h and 100 km/h. However, between 80 and 90 km/h is considered the best. It provides for better reaction times, and shorter stopping distances. Every 1 km/h decrease in average speed reduces crash risks by 3 percent and reduces fatalities by 4 to 5 percent.

Motor vehicles have active and passive safety devices and features, to a lesser or greater extent. The active safety features (to prevent crashes) include – electronic stability control, automatic braking system, automatic emergency braking, blind spot monitoring, lane departure monitoring, adaptive cruise control, rear view cameras and cross traffic alert systems.

The active safety features (to protect passengers during a crash) include – various types of seatbelts and airbags, crumple zones, head restraints, collapsible steering columns, antilock brakes, and safety glass.

However, with or without these modern features in some automobiles, they can all be rendered barely effective or ineffective when there’s a moron behind the wheel. Under such circumstances, serious, possibly fatal crashes will occur.

When crashes occur, the part of first impact comes to a halt, but the rest of the motor vehicle continues to move. This causes deformation, seatbelts tighten, but the head and neck continue moving. All this happens in 0 to 50 milliseconds. Since human beings [involuntarily] blink in about 100 to 400 milliseconds and [consciously] blink in about 572 milliseconds, that initial part of the crash occurs faster than anyone can blink.

In the next 50 to 100 milliseconds, the torso has been restrained by the seatbelt, airbags deploy at about 322 km/h, the head continues moving and the neck will bend. At this point, the chest is being compressed by the seatbelt. In 100 to 150 milliseconds the chest is compressed even further, and the neck and head have both reached maximum flexion. Now, the internal organs are experiencing significant forces. All that has taken place faster than you can blink voluntarily.

Over the next 150 to 200 milliseconds the car rebounds and slows down, so too do the head and neck. The internal organs begin to settle back into place. Over the next 300 to 500 milliseconds, the vehicle and body have stopped moving. depending on the speed at the moment of impact, potential sequels include whiplash, seatbelt burn, air bag injuries, head injury, fractures, damage to internal organs, ejection, lacerations, traumatic amputation, or death.

Death can occur much faster than anyone can blink when poor decisions are made while driving.

Garth Rattray is a medical doctor with a family practice, and author of ‘The Long and Short of Thick and Thin’. Send feedback to columns@gleanerjm.com and garthrattray@gmail.com.