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Whatever you do, please do not even consider this as an option! Recent studies and investigations conducted in the U.S. and here in Ontario have shown that the areas under an over/underpass are very dangerous as the winds are forced through a smaller space intensifying their effect. In the smaller spaces, the winds are funnelled into a tighter space causing an increase in wind presure much like the water from a garden sprayer.
A number of years ago, a news crew was caught unaware of a fast approaching tornado coming along the highway. While they decided that they would film it, it soon became obvious that it was headed right for them. After attempting to flee from the on rushing tornado, they took refuge under a bridge and guided a father and his frightened daughter to take cover under the girders. That piece of film has been used extensively for years as an example of a place of refuge in a tornado, but now people are dying because of it.
What was not said in that film footage is that the tornado that they were dealing with was probably less than an F1, a small one. It has been proven that under a highway over or underpass, a bridge or any similar small space that the winds intensify dramatically and in a larger storm anyone caught under it will be blown or sucked out and into the debris surrounding the structure. In another piece of film footage that is not seen as often, a family of four took refuge under a similar bridge and all that was left of them after the storm had passed was their outlines, sandblasted in mud against the structure of the bridge. In yet another incident, a mother pushed her child up onto a ledge under a bridge and she was pulled out and killed. They found her body a number of hours later under a pile of debris.
Essentially, if all else fails and there is no where else to go, get out of your car and find a ditch or other low lying area and lie down, cover your face and head as best you can. You have a far better chance of survival. It has been proven that lying in an open ditch is your better option. The winds recorded at ground level are much lower than just a few feet above. Also, by staying low, you will avoid much of the debris that is flying around. It can be a terrifying time to find yourself caught out like that but fight the urge to run for the seemingly big, strong bridge structures. Their small spaces can become a place of death and not salvation.
Another example where the information in this booklet has gone wrong is in the first paragraph. It states that "They can cause tremendous destruction with wind speeds of up to 500 km/h or more." While this is true, it is also extremely rare. The highest recorded wind speed was during a tornado in the U.S. a few years ago at 319 mph or 510 kph and based on physics, the maximum wind speed attainable on earth is 512 kph or 320 mph. According to the best information available, there has never been a tornado in Canada with winds speeds that high and rarely in the U.S. do they see those wind speeds. In Canada, we can expect to see tornadoes in the F0 and F1 range most commonly, while there will be the odd F2 or F3. Anything larger than that is most rare in Ontario and Canada as a whole, but are possible as in the Barrie, Ontario, Pine Lake and Edmonton, Alberta tornadoes. The following list outlines the Fujita scale as developed by Ted Fujita, one of the worlds foremost researchers on this subject.
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They have not explicitly stated that it is an unsafe practice but there is more than sufficient research data to state that it is a dangerous place to go.
However, they did not add that taking refuge under an over/underpass was bad thing to do so in effect, they are still wrong but this time by way of omission.
Stephen Mayne Lanarkweather.org
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