Que faire en cas d'orage ?

Une croyance populaire veut que rouler à vélo durant un orage ne soit pas vraiment dangereux car les pneus vous isolent du sol et il n'y a donc pas mise à la terre.

Le moins qu'on puisse dire c'est que cette opinion ne fait pas l'unanimité !

Sur le site Internet du Conseil canadien de la sécurité on indique clairement :

Si vous êtes à vélo, à motocyclette ou sur un VTT, descendez.
Les pneus en caoutchouc ne vous protégeront pas.

Et on vous indique ensuite quoi faire.

Sur le site de l'Association Protection Foudre, dans les 20 recommandations en cas d'orage, il y a plusieurs conseils et explications intéressantes.

Entre autres on apprend que si une automobile close constitue une excellente protection, (à condition qu'elle ne soit pas décapotable oàtoit en plastique), ce n'est pas tanàcause des pneus qui isolent la voiture du sol que parce que l'automobile close constitue une excellente cage de Faraday.

• Si il est impossible de s'abriter dans un édifice (en s'abstenant de s'appuyer contre ou de toucher un pilier ou un mur si l'édifice n'est protégé par un paratonnerre), il faut s'éloigner de son vélo et ne jamais se tenir debout les jambes écartées, ni marcher à grandes enjambées. On risque alors d'être commotionné, voire électrocuté, par une "tension de pas".

• La meilleure position consiste à se pelotonner au sol, après avoir étendu sous soi un ciré ou toute autre pièce en matière isolante (par exemple en plastique). Si l'on ne dispose pas de pièce isolante, la position couchée, jambes repliées sous soi, reste la position de moindre risque.

• Des personnes se trouvant en groupe doivent s'écarter les une des autres d'au moins 3 mètres, pour éviter le risque d'un éclair latéral entre deux personnes.

• On doit s'écarter d'un arbre isolé et de toute structure métallique, notamment de pylônes, de poteaux, de clôtures, afin de ne pas être victime d'une électrocution par "tension de toucher".

En anglais, nous avons trouvé les conseils qui suivent sur le site de la League of Americans Bicyclists.

On y précise que A PREPAREDNESS GUIDE for severe weather is published by the U.S. National Oceanic and Atmospheric Administration/National Weather Service. The following is our adaptation of that guide to specifically address cyclist concerns. National Weather Service has reviewed and approved this adaptation.

• Cyclists on the road are most at risk from thunderstorms if they are under or near tall trees, are on or near hilltops, or are themselves high points on flat terrain (such as crossing an open field).

• Lightning often strikes outside of heavy rain and may occur as far as 10 miles away from any rainfall.

• Rubber-soled shoes and rubber tires provide NO protection from lightning.

• If you can hear thunder, you are close enough to the storm to be struck by lightning. Look for safe shelter immediately !

• When skies darken, look AND listen for increasing wind, flashes of lightning, sound of thunder.

• Lightning remains a danger even when a thunderstorm is dissipating or has passed by.

When thunderstorms approach
• If you are on a hill with exposure to the sky, try to head downhill, seeking out an overhanging bluff or a valley or ravine where you can lower your exposure.

• Move to a sturdy building or shelter if there is one within reach (such as an underpass, a large barn, a store or railroad station). Do not take shelter in small sheds or under isolated trees.

• However, get to higher ground if flash flooding is possible where you are (such as by a creek bed).

If caught outdoors and no shelter is nearby
• Find a low spot away from trees, fences, and poles. Make sure the place you pick is not subject to flooding.

• If you are in the woods, take shelter under the shorter trees. (Lightning is more likely to strike the tallest trees.)

• If you feel your skin tingle or your hair stand on end, dismount fast, get away from your bike, and squat low to the ground on the balls of your feet. Place your hands on your knees with your head between them. Make yourself the smallest target possible, and minimize your contact with the ground.

Le Conseil canadien de la sécurité indique que « un million de fois plus puissants que le courant électrique ménager, les coups de foudre peuvent être mortels. La foudre tue plus de gens dans les pays développés que tout autre phénomène naturel. Un coup de foudre peut causer un arrêt cardiaque lorsque le courant pénètre le corps; il peut aussi endommager des organes, causer des brûlures et, parfois, entraîner des effets à long terme. Au Canada, la foudre fait de cinq à six décès chaque année et blesse gravement 60 à 70 personnes. »


13 août 2009

5 ways to reduce lightning risk

A woman triathlete was struck by lightning last week just 2 miles from the end of a long training ride in Colorado. The bolt knocked her to the pavement. When she woke up to people standing over her, she couldn't move her arms and her vision went dark.

The good news is that she got in her miles before being blasted. Terri Menghini, 44 and the mother of 5, has recovered from the lightning's frightening effects and has only road rash, a cracked helmet and a heckuva story left over from the incident.

She's lucky. On average, 73 Americans are killed by lightning annually and hundreds more suffer debilitating injuries.

About 22 million lightning bolts hit Earth each year. According to stats from National Geographic News, the odds of being struck in the U.S. in any year are 1 in 700,000. The odds of being struck during a lifetime are 1 in 3,000.

About 10% of lightning victims die. Another 70% suffer serious long-term effects that can include brain damage, personality changes, sleep disorders, numbness, dizziness and weakness.

That's all nasty news. And yet as bike riders in the summer thunderstorm season -- perched on a mostly metal object out in the open -- we're susceptible to joining Ms. Menghini as a lightning statistic. Not all outcomes are as happy as hers.

Here are 5 ways to reduce lightning risk :

Obey the "30/30" rule. When lightning is seen, count the time until thunder is heard. If it's 30 seconds or less, seek shelter immediately. Storms can move at 50 mph (80 kph). Stay protected for 30 minutes after the last rumble of thunder because lightning can occur 10 miles (16 km) from the storm center.

Get inside. The safest places are a substantial building or a car with a metal roof. As the National Weather Service advises, "When thunder roars, go indoors."

Get down. If you're caught in the open, get into a ravine or ditch. If there are none and bolts are hitting all around, get away from your bike and make yourself small by squatting on the balls of your feet or kneeling with your toes touching the ground. Experts say this posture may prevent lighting from passing through your heart. Get down right now if a thunderstorm is near and you feel your hair stand on end.

Avoid lone trees and isolated stands of trees. Low bushes are safer shelter.

Avoid metal objects. This includes fences, guardrails and especially anything tall such as flagpoles and power stanchions. It also includes your bicycle. Even carbon bikes still have some metal.


nouvelles achat & entretien rouler au Québec hors Québec sécurité course cyclos montagne industrie quoi d'autre ?

une page mise en ligne par SVP

Guy Maguire, webmestre, SVPsports@sympatico.ca
Consultez notre ENCYCLOPÉDIE sportive

veloptimum.net