A properly-installed guardrail was struck on Southminster Bourne Road southwest of London, Ontario on December 26, 2018 yet a fatality still occurred. What caused this fatal result to the 27-year old female driver is unknown. No photographs were made available by the local news media showing the damage to the vehicle and police have yet to provide an explanation why the fatality occurred.
Initially local news media reported that the vehicle struck a “bridge barrier”. This was not helpful because this did not provide a clear indication of what was struck. Subsequently the site was examined by Gorski Consulting on the morning of December 27, 2018 and this provided a clearer indication of what occurred.
The photo below shows the collision site which is on the north side of Highway 401. Because of the meandering character of Southminster Bourne Road the actual travel direction of the vehicle at the accident site was eastward even though the road crosses Highway 401 which runs from north-east to south-west.
The case vehicle was eastbound on Southminster Bourne Road and approached the left curve shown in the background. The overpass to Highway 401 can be seen in the background.
Some posts are visible along the right side of the road and these would normally be accompanied by a cable barrier. Even though the cable was missing it was not a factor in this collision as it was not involved the collision events.
The physical evidence leading to the collision was classic of what has been observed over several decades of hundreds of similar cases. As the vehicle entered the left curve its right side tires travelled off of the paved surface and onto the gravel shoulder. This caused a counter-clockwise rotation causing the vehicle to begin sliding sideways, leading with its right side, as it crossed the roadway centre-line and then impacted the guardrail on the opposite side of the road just before reaching a small bridge.
The photo below shows the right edge of the road and here it can be seen that a substantial width of additional pavement exists to the outside of the white, painted, edge line of the lane. In the past such an additional amount of pavement did not exist along most rural highways and this led to many loss-of-control events. So because of this additional width of pavement this road segment could be classified as well-designed and equipped.
A substantial width of additional pavement existed to the right of the white painted edge line and this is an additional safety feature that would normally reduce the number of loss-of-control rotations and subsequent collisions.
As typical there was a moderate super-elevation in the eastbound lane leading through the curve. Such a super-elevation involves raising the right edge of the lane so that a lateral down-slope in created toward the centre-line. This “banking’ feature creates an additional lateral force that helps to pull the vehicle to the left and makes it easier for a driver to pass through the left curve. Often the right shoulder at such a super-elevation is not raised like the pavement but is sloped in the opposite direction. This causes a difficulty when the right side tires of a vehicle travel from the paved surface which is super-elevated, to a gravel surface which is not. In addition the gravel produces more drag on those right side tires causing an initial, slight, pull to the right which is sometimes counteracted by a driver steering to the left. Thus these are some of the complicated forces that exist which lead to an eventual counter-clockwise rotation.
The photo below shows the area where the vehicle left the right shoulder and slid across to impact of the guardrail on the opposite side of the road. In the pavement one can see the curved “yaw” marks that were generated as the vehicle proceeded through its counter-clockwise rotation. Typically the most visible tire marks are produced by the two right side tires because the weight of the vehicle is transferred to them during the rotation and deceleration. As the rotation progresses the observer then begins to see the markings from the two left side tires which are usually fainter.
The obvious sign that the vehicle entered into a counter-clockwise rotation is the visible “yaw” marks on the pavement leading to the guardrail impact on the opposite side of the road in the background.
With the advent of event data recorders it is possible to determine the travel speed of the vehicle before the vehicle entered into the yaw. Because such speed data is often related to the rotation speed of the tires investigators must be careful in properly interpreting such data. For example it is possible for a vehicle sliding sideways at 100 km/h to register speed data that indicates that the vehicle is stopped.
Investigators have always had the ability to measure the curvature of yaw marks and determine the vehicle’s speed. Also the angle of lateral striations within the marks can also indicate whether the vehicle was being braked or was being accelerated.
The photo below shows that the yaw marks converge meaning that the vehicle has rotated to a position where it is sliding sideways, leading with its right side as it approaches its impact with the guardrail.
This photo shows that the yaw marks from the rear tires converge before reaching the guardrail and this means that the vehicle has reached a point where it was sliding sideways, leading with its right side, just as it approached the guardrail.
The photo below shows how the guardrail was displaced as a result of the impact. The anchorage posts became separated and deformed. All this is precisely what the system was designed to do. Through its deflection the system provides more time for the striking vehicle to reduce its speed. The destruction of the rail and posts is designed to remove the kinetic energy that exists in the striking vehicle as a result of its mass and velocity.
The guardrail was struck just before the vehicle reached the bridge. The rail was displaced as it is designed to do.
The photo below shows that the guardrail was properly anchored to the concrete bridge abutment and there were additional anchorage posts as the rail approached the concrete abutment. This stiffening of the rail is what is supposed to deflect the striking vehicle away from the immovable and dangerous concrete abutment. In olden days guardrails were poorly constructed such that they were not properly stiffened nor anchored to bridge abutments. As a a result vehicles that struck the railing were often chanelled into an impact with the abutment resulting in fatal injuries. Such an incident occurred on Highway 401 at Dodd’s Creek, just west of London in the late 1970s resulting in an inquest. As a result of that inquest the Ontario Ministry of Transportation began a review of its guardrail anchorages and it was mandated that all guardrails should be anchored in the manner shown in these photos.
The guardrail system is purposely designed with additional posts near its anchorage at the concrete bridge abutment. This is what re-directs the vehicle away from the dangerous, immovable abutment.
The backside of the guardrail is shown in the photo below and it provides a further view of the stiffening of the rail as it approaches the concrete bridge abutment.
This backside view of the guardrail shows how it has been stiffened by an increase in the number of anchorage posts as it approaches the bridge abutment. Again, this stiffening is meant to deflect a striking vehicle away from the immovable concrete abutment.
While the vehicle was deflected during the initial impact it also continued to rotate counter-clockwise and therefore its rear end struck the railing of the bridge further to the east as shown in the photo below.
View of the metal bridge railing where the rear of the rotating vehicle made contact after its initial contact with the guardrail.
The presence of this additional, secondary contact may explain why the local news media indicated that the vehicle struck a “bridge barrier”. While it is true that the railing was struck this secondary contact was of minimal consequence as the main threat was from the initial impact with the guardrail.
The physical evidence showed that after the initial and secondary contacts at the north side of the road the vehicle was deflected back toward the south where it made an additional, minor contact with the bridge railing and then settled to rest near the east end of the bridge, as shown in this photo.
The official reports of the incident indicated that it was the vehicle driver who sustained fatal injuries while a right front passenger was transported to hospital with serious injuries. This is not what one would expect from this collision. Since the direct impact occurred at the right front of the vehicle it was the right front occupant who should have been in greatest danger of sustaining the higher severity of injury. The reported driver of the vehicle should have been located at the far side (left) of the vehicle interior when the vehicle struck the guardrail and therefore it would be expected that she should sustain less injury than the right front occupant.
As stated earlier, regardless of where the occupants were positioned fatal injuries would not be expected to occur. The very purpose of a guardrail is to reduce the severity of injury and the deflection of the vehicle that occurred should have provided both occupants with a good opportunity to survive this impact. This is another example where the public needs to be better informed about these incidents. The death of a person cannot be a private matter when the reason why that death occurred is in question. There could be factors that could explain why the fatality occurred but an explanation should be made publicly by those who conducted the official investigation.
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