The crash that killed Princess Diana in 1997 is related the minor collision shown in the photo above. But why? Surely they are totally different in severity and consequence. Yet they both exemplify the working of technology that often protects, while sometimes it kills.

Thirty years ago vehicles rotated when they when out of control and, invariably, they slid sideways and struck a roadside object or went into a lateral rollover. While these events still happen electronic stability control (ESC) now prevents that pre-crash rotation in a vast number of instances. While many say that this prevents collisions that comment is not totally accurate. It prevents some collisions but it alters others. Thus some collisions still happen but now they happen with the vehicle’s front end, not with its side.

As with any safety device this works well for the vast number of incidents. But just like air bags, seat-belts and everything else, sometimes modern technology makes things worse. The old saying is still true: “Give me the collision you will be involved in and I will select the car or safety device you need to have”. The obvious problem is that we do not know what type of collision we will encounter. And sometimes the safety device becomes your enemy because you happened to be one of those rare instances where the technology was not meant for that crash.

So how is this similar to Princess Diana’s crash?

When her Mercedes was involved in a glancing impact with a Fiat Uno this should have caused a rotation and Princess Diana’s vehicle should have slid sideways when striking the unprotected tunnel pillar. By some fluke of luck the impact could have been to a part of her vehicle that was further away from its centre-of-gravity and therefore the severity of that impact would have been reduced. The Mercedes would have spun further down the road and might have struck other objects but it was the initial impact with the tunnel pillar that was crucial.

The problem is that Princess Diana’s Mercedes was equipped with an earlier version of mechanical stability control that stopped the Mercedes from rotating and caused it to travel toward the tunnel pillar with its front end. But because the impact was so close to the Mercedes centre-of-gravity the change-in-velocity was much greater than if it was involved in a glancing blow during a sideways slide. So in this rare instance the technology did not help, it likely made the collision worse.

So what do we see in the above photo? A vehicle that was travelling through a curvy crescent in the Town of Simcoe and the driver likely lost control. But there was no pre-crash rotation (Look at the tire marks in the snow leading to impact). This is a common occurrence when ESC kicks in. Sure the collision was of minor consequence but it helps to know what things were like a long time ago, how they have changed, and why it matters.

If the impact was to the driver’s door the driver could have died. Yet it was such a minor collision wasn’t it?

“Minor” depends on so many things.