Although the most severe, head-on collisions also provide the greatest opportunity to use the structure of vehicles in riding down the destructive forces of that impact. This was clearly shown in the OPP photo shown above, relating to a serious head-on that occurred on Hwy 86 in Huron County, northwest of Listowel, Ontario on March 19, 2020.

It is helpful that the OPP frequently provide a photo or two during their notifications of serious collisions in Ontario. While a single photo is far from adequate, it is better than none, as was frequently the case only a few years ago. Even the availability of a single photo can say a lot about what has taken place. While we do not have the advantage of examining the vehicles, the collision site, or even additional crucial photos, we have the advantage of having examined hundreds of similar collisions over the past four decades.

Firstly, in earlier times, before the advent of electronic stability control (ESC) and similar technology, the patterns of vehicle crush could help the investigator in determining the pre-crash circumstances of a head-on collision. As someone who spent many long hours in a towing compound measuring the crushed state of vehicles, and then returning to the office to creature large-scale diagrams of those crushed shapes, the patterns of vehicle crush and specific “points-of-mutual-contact” said a lot about what happened in the few seconds before impact. Now so-called “experts” simply examine the contents of an event data recorder (“black box”) and they know precisely what happened because the box tells them so. But they need to know nothing about the physical evidence on the vehicle. That places a lot of blind faith in the validity of the numbers in the box.

In the past, many head-on collisions could be grouped into two classes: 1) Those with crush patterns that were identical, look book-ends and 2) Those with one vehicle exhibiting additional crush along its side, primarily its right side.

In the first instance the book-end patterns of crush (exhibited in the two vehicles shown in the above photo) occurred in passing situations where a driver misjudged a return to their own side of the highway resulting in an off-set impact with maximum crush at the left (driver’s side) of each vehicle. The offset involved direct contact to 50 % or less of the left portion of the front ends. This would result in counter-clockwise rotation of both vehicles and spin-off to final rest, generally on opposite sides of the highway. When these collisions approached high severity the probability of structural intrusion into the driver’s space increased making it more difficult to protect drivers, even when seat-belted. As time as moved on Federal compliance tests and even those by the insurance industry (Insurance Institute for Highway Safety – Highway Loss Data Institute) caused improvements to be made in such offset frontal impacts resulting in less structural intrusion and better ride-down as a “system” of safety features worked together. Air bags were a giant improvement when they became depowered in 1998. So the seasoned investigator who came upon a collision site could have an instant understanding, although preliminary, of what might have led to this type of crash. But now-a-days things are a little different.

In the second instance, the pattern of crush involving one of the vehicles with direct damage to its side, was indicative of a loss-of-control situation by the vehicle with the damage to its side. Very often such events occurred not to far from a highway horizontal curve and sometimes the drop-off of the right side wheels off of the right pavement edge, before commencing a counter-clockwise rotation into impact. While many such collisions involved this single and direct rotation, many of these events involved multiple rotations, clockwise and counter-clockwise, as the driver made attempts to regain control before finally sliding into the front end of another vehicle in the opposing lane. Unfortunately the cause of these events was difficult to locate because the initiation of the loss-of-control occurred very far from the actual impact and because there was no physical evidence generated the substantial distance in the early portion of the driver response. Very often signs of a vehicle travelling onto the right shoulder were destroyed as good intentioned passers-by stopped on the shoulder and destroyed that evidence with their tires. The evidence was destroyed further by police and other emergency vehicles as they came to a stop on the shoulder to attend to the victims.

Severe, head-on collisions are also characterized by short, post-impact travel distances to final rest, often less than 10 metres. This is differentiated from angle impacts at intersections where those travel distances may be in the range of 25 to 50 metres.

Obviously there are many varieties of head-on collisions besides the two that have been mentioned. A detailed exploration of crush patterns is rarely a part of a police reconstructionist’s duties as now-a-days independent reconstructions requested by insurers and other agencies are a rarity. As mentioned earlier, reconstructions have become more and more reliant on the downloading of event data from a vehicle’s “black box” and little focus on collecting and understanding of the details of the physical evidence.

It the advent of electronic stability control (ESC) and other advances, the motions of a vehicle approaching impact are increasingly controlled by vehicle sensors and computer logic and thus the two patterns of head-on collisions become murky in their interpretation. The unfortunate reality is that, while in most instances the computer logic leads to an improvement in safety, at times that logic is limited such at collisionsĀ  become more severe. The photo above provides an opportunity to discuss this problem even though it may not have occurred in this specific instance.

The oddity about the evidence shown in the above photo is that the direct contact damage is almost fully across the front ends of both vehicles. This is odd because, in the past, it was difficult to achieve. Such occurrences were created when one driver or both madeĀ  very poor judgments about how to avoid the collision. This would occur for example when one of the driver’s judgments was badly impaired or in instances of poor visibility or poor road surface conditions. Most head-on collisions occurred with 60% or less of frontal offset and it was difficult to find a collision with more. So in the present instance, if this had occurred 30 years ago, we would view it as rare. But those vehicle sensors and computer logic changes that.

Now, as drivers attempt to introduce massive steering, braking and acceleration inputs, the vehicle computers increasingly become the “Big Brother” making the final decision as to how the vehicle’s pre-impact motion will be altered. The computers believe that the greatest benefit to the driver is to keep the vehicle pointing in the direction where the vehicle is travelling. And that makes since if the collision is inevitable and we want to use the full length of the vehicle’s front distance to crush and protect the occupant. But in this attempt some collisions may become more severe as there is greater overlap between vehicle front ends and the impact force is closer to each vehicle’s centre-of-gravity. This is the Princess Diana syndrome that has been discussed before, wherein the force of the tunnel pillar impact was substantially toward her vehicle’s centre-of-gravity. So what we see in the above photo is that, with the very large overlap there is very little post-impact rotation and very little post-impact motion to final rest. Essentially all of the pre-impact kinetic energy was dissipated by the vehicle crush and none was dissipated by post-impact factors.

Even the most inexperienced novice could recognize that the centre of the debris located between the vehicle front ends is where the point of impact occurred. General observations that the two vehicles were of relatively similar mass, indicate they were likely travelling at similar speeds. The deployment of side curtain air bags would suggest some lateral force which may not be unusual given that such impacts cannot be precisely at 180 degree closing velocities.

So was this collision affected by the vehicle’s sensors and computers? An assessment of the recorded data would provide that answer but we will never be provided with that information. While this is kept secret amongst the very few police and insurance investigators officially assigned to the case, the public also has a stake in this. It is the public who will be involved in the next fatality-producing impact yet the public is not entitled to know what it is that will kill them. Oh yes, your doctor will tell you the drug he is giving you will make you better but you are not entitled to know when that drug contains a poison.