It may be of little interest to the general public that a car reportedly struck a pedestrian in a school zone and then struck a utility pole. But to an accident reconstructionist the facts are intriguing.
It has been reported that yesterday afternoon a Nissan Altima was travelling westbound on Central Street in Waterloo, Ontario and it was passing the area of the MacGregor Public School. In this zone Central Street is governed by posted 40 km/h maximum speed signs. It is also interesting that the Nissan driver would likely have made a turn onto Central Street from King Street, less than 200 metres away from the location where the Nissan struck a utility pole located in front of the school. One would think that, along with the posted speed, and the required turn, the Nissan should have been travelling rather slowly.
The Google Maps views of the site (shown below) also show that parking is allowed on the opposite side from where the school drop off zone thus narrowing the passage between parked cars and vehicles, such as school buses, that drop off or pick-up students. So this narrowing of the available road width would also tend to slow the speed of through traffic.
A quick measurement, using Google Maps, of the lateral location of the struck pole, indicates a distance of about 6.5 metres from the roadway curb. In terms of roadway design that 6.5 metres is sufficient to conclude that a vehicle would not be expected to travel such a lateral distance, especially in such a low-speed zone. Yet the impact to the pole was not minimal, as shown in the photo below taken by David Bebee of the Waterloo Region Record Newspaper, and the driver’s side airbag had deployed.
The frontal impact to the Nissan is also interesting. Due to the installment of electronic stability control (ESC) the likelihood of pre-impact yaw (or “fish-tailing”) has been greatly reduced. Yet ESC does not guarantee avoidance of an off-road collision, it only means that if the collision occurs the vehicle will likely be pointing in the direction it is travelling rather than sliding sideways. And so this result is exemplified in the above photo. Where, prior to ESC, we would expect to see such a vehicle struck the pole with its right side, now the impact is to the front end. In many instances an impact by the front end of a vehicle is better than impacts to the side, but that topic is for another day.
We may assume that the Nissan was travelling along Central Street, encountered a pedestrian, and then veered off the road and struck the pole. But many complicated things can happen other than what is initially believed. For instance the Nissan could have been stopped on the Central Street and an unintended acceleration could have occurred, either due to driver error or due to a problem with the vehicle. Limited visibility could have been an issue due to a school bus such as the one shown in the Google Maps views of the site. Maybe something else caused the driver to veer off and strike the pedestrian walking on the sidewalk. In reconstructing the circumstances we can look at the angle of the path of the Nissan. Vehicles travelling at high speeds are not capable of changing their travel direction or pointing as much, in a given distance, as vehicles travelling at slow speeds. And, given a number of previous investigations, an experienced reconstructionist can use such past cases to consider what angle would be common and expected. When physical evidence of tire marks, scrapes and damage to grass is available more detailed opinions can be expressed. But even without that physical evidence, the pointing angle at impact, or the rest angle of the vehicle, can be of some assistance. The quality and detail of the conclusions is dependent of many details, some of which can be obtained directly, while in other instances the details have to be derived from further analysis and testing. In many instances the details that are only available to the police need to be obtained in order to consider what matters were relevant.
It was reported that the struck pedestrian was a 43-year-old female so, at least we know that the collision did not involve a school age child. But did it involve a school crossing guard or a parent or teacher? Given the location of the collision in front of a elementary school there is more concern about the potential safety of children regardless of who was struck because this result may provide some clues about unexpected safety problems that have not been detected.
These are many interesting questions to persons such as myself who conduct detailed assessments of motor vehicle collisions. Rarely are there sufficient facts reported in official news media for me to be capable of providing a full and conclusive opinion about what factors may be involved. But in many cases some suspicions are always present that may not be recognized by the general public.
UPDATE: April 26, 2019; 2340 Hours
Additional information has been made available through local news outlets in the Kitchener-Waterloo area. Regrettably, the female pedestrian who sustained fatal injuries in the crash was identified as Leanne Holland Brown, a Dean of Students at the nearby Wilfrid Laurier University in Waterloo. She leaves behind a husband and two sons. Details like these demonstrate the tragedy that exists behind the cold hard facts that I often work with.
The news media quoted police in saying that the Nissan “went out of control” and then struck Brown who was reportedly located on the sidewalk at the time of impact. This leaves some further questions in my mind.
Even if the Nissan was travelling 50 km/h, which is 10 km/h above the speed limit, at the time that the loss-of-control occurred, one would normally expect some speed loss in travelling from the road to the sidewalk, such that it is not fully explainable why the fatal injuries occurred. In the normal scenario of an upright, adult pedestrian struck at a speed of less than 50 km/h fatal injuries are not common unless there are special circumstances. One special circumstance would be if there was a head impact to a stiff portion of the vehicle such as an A-pillar. The A-pillar is a stiff, metal pillar that is located at the side of the windshield and essentially holds up the roof of the vehicle. There can be a large difference in the severity of a head injury if a pedestrian is fortunate enough to make head contact with the windshield or the centre of the hood which are generally more forgiving. Researchers know these facts and attempt to develop vehicle designs to lessen the chance of a head impact with a stiff portion of a vehicle’s perimeter.
Even when an A-pillar is struck it often occurs after there has been an initial contact with a frontal portion of the vehicle such as the bumper, hood or fender. In such a situation the body of the pedestrian has already been accelerated, from that initial contact, such that the severity of head impact with the pillar is not as severe as a situation where there is only head contact.
Whatever the precise mechanism of contact and source of injury, the bottom line is that a fatal consequence should be not be expected and further inquiry would be necessary to understand what transpired.
It is not clear what is meant by the term “loss-of-control”. Such a description most often means a loss of directional control. But it may mean something different that has not been explained. One possibility it that the comment refers to a loss-of-control of the speed of the vehicle.
If there had been a sudden, unintended acceleration one would expect that the vehicle would be travelling faster at the pole impact than at the pedestrian impact. Although the single photo of the damaged Nissan hides the extent of frontal damage it is my suspicion that this vehicle did not sustain a speed loss greater than 50 km/h from the pole impact. Thus the Nissan would have to be travelling slower than that speed if the pedestrian was struck earlier in time when the acceleration should not be reached its maximum. Furthermore, there would have been clear evidence on the sidewalk and grass of spinning tires which would clearly confirm the acceleration. Depending on the year of the vehicle an event data recorder (often called a “black box”), may have recorded the several seconds of impact and this would also confirm whether an unintended acceleration occurred. Police would normally use a specialized Crash Data Retrieval kit to download the data except that many Nissan vehicles are not compatible with that equipment and contact of the manufacturer might be required.
Overall the reported events represent an intriguing scenario that would not be satisfactorily resolved without additional detailed information such as on-site photos, measurements, witness and driver statements and a full examination of the vehicle that would normally be obtained in a police investigation.
The best that can be hoped for is that the official investigators can perform their duties in a way that provides the proper unbiased answers to these many unresolved questions.