Median barriers that are too low cause heavy vehicles to rollover and increase the severity of collision consequences. Such was the apparent case in a double-fatal collision that occurred on the eastbound Highway 401 at Dixie Road last evening, August 11, 2019. Preliminary comments by the OPP indicated that a Corvette was changing lanes when it made contact with a tractor-trailer. The driver of the tractor trailer lost control and struck a Mazda vehicle before rolling over top of the concrete median barrier and catching fire. A photograph showing the Mazda and Corvette was distributed by the OPP and is shown below.
One can expect that operations by emergency personnel will cause damage such as the removal of the roofs of the involved vehicles. Yet there is evidence of collision damage visible at the upper levels of both vehicles which is not consistent with typical emergency personnel procedures. While it is possible that rollover events could cause some of this upper level damage, the “tearing” characteristics of the sheet metal is not typical of rollover events. Thus it is quite likely that the substantial upper level damage to both vehicles is from interaction with the tractor-trailer. Large chunks of concrete lying in the background of the photo confirms that the tractor-trailer caused considerable damage to the concrete barrier during its rollover.
Whether the fatal injuries to the occupants of the two vehicles could have been prevented remains to be evaluated. However what is obvious is that the low height of the median barrier was inadequate for interaction with heavy vehicles. The GoogleMaps views of the area shown below indicate that the eastbound collector lanes of Hwy 401 are often filled with vehicles of a smaller mass. When heavy trucks and buses exist they are located primarily in the right lanes, away from the concrete barrier. While this may appear to be helpful it is not.
When an impact occurs with a heavy truck in the right lanes it will most likely involve a smaller vehicle such as the Corvette. As such the initial contact is unlikely to reduce the speed of the heavy truck but may cause it to go out of control. This is precisely what the OPP have indicated. However a heavy truck that is out of control in the far right lane and travelling at highway speed will approach the median barrier at a sharper angle that if it went out of control in the lane closest to the barrier. This sharper angle means that the barrier will need to provide greater redirection of the heavy truck than if the barrier was struck at a narrower angle. But when the barrier is too low that redirection cannot occur and the truck rolls over it, as it apparently did in the present collision. If the truck had remained upright it is quite likely that it might sustain minor sideswipe damage and coast to a stop along the barrier. However, with the scraping that would typically occur during the rollover along the top of the barrier this provides the igniting friction that could set off a fire. The results were that the truck caught fire but also the barrier was badly damaged. These consequences led to greater damage to the highway and a major disruption of traffic.
Although the concrete barrier on Highway 401 at Dixie Road is of an older vintage, its lack of adequate height is not unusual. Almost all “W” guard (guide) rails throughout most major expressways in the North America are too low. Consequently any large truck or bus that strikes these systems is in grave danger of rolling over.
This is particularly catastrophic when it involves an intercity bus that may be loaded with 60 or more passengers. Given the much larger mass of such intercity buses their upper structures are extremely weak and any rollover at highway speed is likely to result in many fatalities, as has been shown in many previous incidents worldwide. In a recent brief submitted to the Canadian Parliamentary committee studying bus passenger safety, co-authored by Professor Ahmed Shalaby, of the University of Manitoba, the inadequacy of most roadside barriers was highlighted. Several examples from previous bus rollovers over top of low roadside barriers demonstrated the unnecessarily dangerous consequences that result. Recently, in the U.S., changes are being made to the suggested heights of guardrails to increase their height. Very often Canadian regulators follow the guidelines implemented in the U.S. However it will take many years before any substantial changes can begin to be made to the very large number of inadequate systems that presently exist. Thus the public needs to be aware of these dangers and appropriate measures need to be considered to reduce the chances heavy vehicle rollovers.
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