Comparative Crash Data on Cars

Comparative Crash Data on cars

Impact Type

Cars crashed at 35mph into solid barrier. This is the same as a head-on collision between two identical weight vehicles each doing 35mph (ie, 70mph head-on.) or the same as driving into a parked identical car at 70mph. Impacting in a small car against a heavier vehicle is a clear problem.

Impact Type

A score of 5 means a 10% or less chance of serious injury. Data courtesy of the NHTSA.

The Misnoma

Increasing one's speed by a mere 5mph will negate all the safety benefits of the best car over the worst car due to the non-linearity of speed:crash energy. This vital point is omitted from the majority of crash safety coverage in the media.

A human being can withstand 30-40G before serious injuries result and there is a finite length of crumple zone to dissipate such injury before intrusion into the cabin becomes inevitable due to the energy impulse of the collision. Past 40mph the chance of survival against a same-weight car diminishes rapidly, at 56mph survival is vastly beyond present crash & safety design speeds. The energy at 56mph is approximately 200% greater than at 40mph - not 25% greater.

Vehicle weight is a critical factor in crash survival. A heavy large car with poor crumple zones leaves the occupants to absorb higher G loadings. A light euro-box car impacting a heavy large-car will result in the lighter car (and it's occupants) experiencing a greater change in acceleration than the larger car. For two equally safe cars on ratings, the larger & heavier car will force the smaller & lighter car to absorb more of the impact energy which may result in it's occupants faring worse than statistics may suggest based on purely impact speed.

G-loadings in racing cars are very different to road cars. Racing cars involve very linear deceleration through use of honeycomb aluminium & composites, the decelerations are over long periods through run-off areas or deep tyre walls, full 6-point 4" web racing harnesses & crash helmets are worn, and declerations are often momentary as repeated obstacles are being bounced off.

There is no magic to a racing car. If you hit a tree at 100mph and decelerate to 0mph in 3 feet then the G load experienced is both monumentally large and over an extremely short duration. Headline G figure is nothing without the duration over which it is experienced.

To clarify the importance of safety-belt wearing, a 30G impact will involve you exerting a force of 6,000lbs on the seat-belt. If a seat-belt is not worn you will exert a force of 6,000lbs on whatever object fate chooses for you. Not surprisingly even innocent appearing objects become lethal. Thisis particularly true where rear seat passengers are not wearing a seat-belt and impact the head of the person seated in front of them - or to the side of them. To quantify 30G more directly, it is 30 people standing on your shoulders using your skeleton.

Those who come after you so they stand on your shoulders do not do so all once.

Data courtesy of the NHTSA. A score of 5 or below means a 10% or less chance of serious injury.

Probe does well

Probe/MX6/626 do extremely well on head & chest injury. Leg loads are within limits although this is one particular area that industry wide needs more work. For Femur-load, Head-Injury-Criteria (HIC) and Decelerative-G lower = better.

The problem with most vehicles is their construction: steel is a poor choice as a crushing material in comparison to composites. Composites crush from the point at which load is applied and not somewhere else along their length like steel, and so the survival space can be both better understood in design and maintained during an actual collision. A Corvette which uses both composites & tubular construction provides an example of using both materials to their optimum, the ideal eventually being an all composite car such as GM's Autonomy.

Front firewall intrusion is a common occurency in impacts, where steel crushes at points well behind the point of impact. Intrusion is frequently 20-27cm or more in a frontal 40%-offset impact at 40mph. An old argument for safety used to be a 12" spike fitted to a steering-wheel, what drivers & media alike do not know is that it is fitted - in the footwell.

Intrusion mean femur loads, lower-limb multiple compound fractures, femur multiple compound fractures, pelvic fractures next to internal organs with the complex metal jigs & screws through to bone joining everything back together (if lucky) the result. Thus for any vehicle, wearing a seat-belt properly and placing the seat back (yet still able to drive safely) is very beneficial regarding intrusion and also gives the airbag space to deploy.

In driving you have no control over the distance of the vehicle behind you from your rear bumper. What you do have control over is the distance of your car to the vehicle in front. Thus if the vehicle behind is too close, you correspondingly increase your distance from the car in front. If any event in front then requires you to stop, you have better control over your survivability in terms of distance to stop.