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The Science of Slickness: How and why road crews keep you safe in the snow 

The procedures and chemical reactions that give our icy roads traction.

click to enlarge winter_adventure_snow_plow.jpg
If you've ever bitched about being stuck behind the snowplow or the gravel truck, you should get that attitude of yours in check and realize that these people are trying to keep you alive and your vehicle intact. Most of us acknowledge that, but few of us know exactly how these street scientists are keeping us safe.

Magnesium Chloride
Now that sounds scientific! That is what's called a chemical compound, y'all, and it's what both the city of Bend and the Oregon Department of Transportation spray before, during and after snowstorms.
City of Bend Street Supervisor Kevin Ramsey says that while most of the country is still throwing down a salt-based de-icer, Bend has long favored magnesium chloride MgCl2(H2O), for its effective, yet less-corrosive qualities. In short, that means that it isn't going to mess up your car (or your streets and wildlife) quite as much.

Here's the scientific explanation... and a reason why you should wash your damn car.
"Magnesium Chloride is less corrosive. The bottom line is that whatever we do has the potential of causing damage to vehicles. The biggest thing is keeping your car clean after a storm event," says Ramsey.
One misconception is that de-icer products are only used after a snowfall. Actually, according to the city of Bend, the magnesium chloride is actually applied to street surfaces in the days and hours before weather forecasters project that snow will fall. The chemical then melts the snow as it falls and is also useful in making the snow that's fallen atop the chemical-covered surface easier to remove.
One drawback, however, is the fact that if the mercury drops below 20 degrees, the chemical isn't as effective. Still though, it's better than nothing.
Cinders vs. Rock
For years, the roads of Bend were paved with a film of red cinder dust for most of the winter and spring months. Then, the redness disappeared.
What's up with that, you may ask? Well, some may remember the winter of 2008 which was a long, snowy, icy mess and for that reason the city needed to throw down tons (literally) of cinders. But when the snow melted, the cinder dust was blowing everywhere, getting all up in your business in addition to harming the air quality. The following winter, the city decided to move to a harder, denser rock substance.
Not only has this decreased the post-storm messiness within city limits, but the city is able to more efficiently suck up this material and reuse it on the next storm, says Bend Street Supervisor, Virgil Breeden. He says this has also saved the city money and lessens the amount of rock that's sent to the landfill.
But wait... there's still plenty of red on the roads of Central Oregon, right? Correct. The Oregon Department of Transportation continues to use cinders in the region, according to ODOT's Peter Murphy, who says the department uses a degree of discretion in laying down the red stuff, looking for "critical areas" like curves and hills.
Another reason ODOT doesn't put cinders everywhere, aside from the obvious logistical barriers, has to do with keeping drivers alert.
"We've found that if you put cinders down, driver behavior tends to negate the effect. Speeds go up when we put cinders down and that cancels out the safety aspect of it," says Murphy.
Take 'er Slow, Drive Smart
The city's Breeden and Ramsey, in addition to ODOT's Murphy, all agree that the number one factor in keeping drivers safe is for motorists to take it slow when there's snow or ice on the ground.
"We want drivers to do their job. We want there to be an impression that drivers are on wintery surfaces and to use the appropriate care," says Murphy.
Scientists have found that stopping distances will at least double on a snowy surface - on ice, that distance could be much, much greater. Ramsey says that in addition to making sure you have plenty of distance between you and the vehicles ahead of you when you approach a stop sign or traffic light, there's another trick you can use. By moving slightly to the right when approaching a stop, you'll have more traction.
"The rock moves to the right as more vehicles travel the road. So when you get up to an intersection, move over to the right a bit and you'll have some fresh rock to stop on," says Ramsay.

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