In the winter before last, Dane county spent 1.7 million dollars on rock-salt. But that number may be getting lower in the future
A new report from the Traffic Operations and Safety Laboratory at UW-Madison looks at the effectiveness of brine: a water and salt mixture that’s sprayed onto roads as an alternative to rock salt. It has a higher concentration than the stuff that you might use to pickle cucumbers.
Highway departments across the state already use brine on roads before some storms come, but the new research from the UW Lab confirms that brine is often better than hard road-salt.
The study showed that using brine instead of rock-salt clears roads 2 hours quicker. And because trucks can drive faster when applying brine, some roads can be treated 30% faster.
The Department of Transportation has been strategizing ways to reduce salt use for many years. This report just quantifies brine’s effectiveness. Reducing salt use is important for cost, and the environment. I spoke with Andi Bill, one of the scientists who conducted the study, about the benefits.
“There’s a lot less salt bouncing off the road way onto neighboring fields and lawns. But also as that runoff occurs, we get less salt into our lakes and streams and even our groundwater with it.”
As a liquid, brine can also get into cracks and crevices better than a chunk of rock salt. And brine requires nearly a quarter less salt compared to rock.
But it also requires its own specialized equipment. Right now, not every county in Wisconsin has the ability to make brine. Andi Bill
“They have to have a brine maker. You can think about it as a big mixing bowl. It’s putting that salt and that water together to mix it up. And then they have to have a special tank. And then that tank will feed into a sprayer nozzle that will spray down on the roadway.”
Currently, at least 13 counties in the state have mixers and many more are looking to buy one. Dane county is on the list to receive one this year
Bill also wanted to clear up a misconception about spraying brine.
“Some people are driving behind these vehicles and they see liquid coming out of it. They think that there is just water going on the roadway. So they are concerned that it will cause more crashes because you’re putting water on a roadway that’s already going to freeze, right? So there are concerns over time that it will cause crashes or unsafe events than regular rock salt. We weren’t seeing anything in the crash data, but we wanted to make sure we addressed this misconception and took a look at it.”
The study found that brine-treated roads are safe. The method can, though, accelerate corrosion on vehicles, so it’s best to avoid driving directly behind a truck spraying brine. An undercarriage wash for your car can also help reduce corrosion in the winter.
As highway departments become more comfortable with brine, there’s room to tinker with the different formulas, including sometimes using rock-salt. Bill says a veritable cook book of formulae could help adjust to specific weather conditions.
“It would be nice to have a recipe book for this. So you know that the winter storm is coming, you know you have this temperature and this amount of snow. First of all this doesn’t always happen – things change on us. But being able to say ‘ok this is what we should be putting out there’ and having our storm fighters be ready to do that and be able implement that plan.”
“File:Winter road treatment using salt brine.jpg” by Z22 is marked with CC BY-SA 3.0.