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MADISON, Wis. – It’s a brutal combination out on the roads.
Thursday’s high winds, constant snow, and extremely low temperatures made for messy commute conditions and brought out an arsenal of plows from Madison and Dane County. But they weren’t armed with the same ammunition.
“It all depends on, you know, what you're doing,” Dane County Highway Operations Manager Dan Behrend explained. “We're plowing like the Beltline, the interstate, very high-volume high-speed roads.”
Behrend said the county had 59 trucks out Thursday, all running different routes. His tactics are to scrape the roads as clear as they can get before salting them down, something he said is more successful on highways.
“Every road's a little different,” Behrend said. “What we've got going tomorrow for us though is we do have the sun out again. And that will really help open things up and help our job in clearing the roads.”
George Dreckmann, Coordinator for Madison Streets and Recycling, said combining salt with the very low temperatures can be even more dangerous on city roads.
“It’s kind of like what happens at an ice rink when you run a Zamboni over it. If we're going to put some salt down, we're basically just creating a nice smooth layer of water on top of a frozen surface. That freezes, and whoosh, you've got black ice and you're off the road,” Dreckmann said.
The 32 trucks Madison had rotating throughout the day and night spread sand instead of salt, concentrating on slick areas and intersections. Dreckmann said this is only a short-term fix for temporary traction.
It's not going to do anything to melt the snow, it's not going to do anything to break the bond so that we can get that snow scraped up with our plows. So it's really limited as to its benefits.
Mike Randall with UW’s The Wonders Of Physics Program explained the science behind salt.
“Effectively, you've just lowered the melting point, which is good news for drivers because while wet roads are slippery, icy roads are way way worse,” Randall said.
That said, Randall explained salt only helps thaw out ice or snow on the roads if it’s above 20 degrees or so. He said when it’s any colder than that, there is no liquid water left for the salt to dissolve into.
Randall also demonstrated the fact salt doesn’t release heat, but actually lowers the temperature of the water it helps melt.
So why put salt on the roads?
“Answer's simple. It's cheap! It's really cheap,” Randall said.
Randall pointed out salt is also relatively safe for the environment, but there are pricier alternatives that are better at melting ice that may not be fiscally probable for municipalities.
Dreckmann said sand costs about $10 a ton, while salt runs $69.50 a ton. He plans to start salting city streets once the temperature gets above 20 degrees.
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