Why do They Put Salt on Icy Roads?
For anyone who lives in an area where winter can get very severe, there is the task of dealing with ice on the roads and sidewalks around town. Often, municipalities put down salt on icy roads. What is it about salt that helps make driving conditions safer? Here is some background on the use of salt on roads, and how using salt on a road can make a big difference.
Most people are aware that rain and melting snow can turn into ice. When this ice sets up on the roadways, there is a need to break down the icy layer, making it possible for tires to maintain traction on the surface of the roads. The presence of the salt causes what is known as freezing point depression. That is, salt helps to lower the temperature at which water will freeze.
Placing salt on icy roads helps to inhibit the crystallization of water particles into ice, even as the salt breaks down any ice that may have already formed. The same result takes place in the case of placing salt on sidewalks. The environment is suddenly altered and it is less possible for the accumulated water particles to freeze into a slippery and dangerous layer of ice.
Along with melting ice, placing salt on icy roads also helps to provide a bit of traction for the tires even as the ice is beginning to melt back into water. The grainy nature of the salt allows the treads on the tires to grip the surface of the road, thus minimizing the chances for sliding or fishtailing on the road. Of course, drivers still have to be very careful about applying the brakes while the salt is working its magic on the ice, but at least the use of salt helps to lessen the opportunity for accidents to occur.
When it comes to the need to melt ice of a street or major thoroughfare, nothing beats the use of salt. There is not even a need to use a concentrated form to do the job. In many places, plain old sodium chloride or table salt is regularly employed when there is a need to melt ice from roads and sidewalks. As an inexpensive means of maintaining the safety of persons during freezing weather, nothing can beat the use of salt to keep icy roads and sidewalks under control.
There's no salt on the roads in Alaska.
I am from Chicago. I moved to Atlanta. Here in Atlanta, they completely freak out over snow. They throw sand for some odd reason on the streets and I don't know where they got the idea but it is completely ineffective over ice. You're just sliding over the ice and pushing sand around. This is why the whole city was shut down a few years back because of the ice.
I never remember them using sand up north. It was always rock salt that broke the ice up and allowed easy breaking up because the salt actually melts through the ice and loosens it up. I don't know if they're being hard headed, but why not take advice from northern cities that deal with this on a regular basis. Sand does not work whatsoever on ice, period. Use salt.
I'm from the south but I've driven everywhere. I totally agree that southerners flip out about the snow. I don't think you acclimate back and forth, though. I think it's just what they're used to. Since I've driven everywhere, I can deal with more inclement conditions. Also, if there are only a couple of days in the year that it concerns you, why even take a chance? You don't want most of these people out on the roads anyway. Such a large collective of non-snow drivers actually would make it a lot more dangerous.
There's just not enough time where the roads are bad for people to learn, but no one around here asks why they use salt on the roads. I'm actually surprised that anyone who lives anywhere it snows wouldn't be aware of this. The process is the same everywhere I've been. A large truck comes through with a plow on the front and salt or other mixture coming out the back.
In the Northwest I noticed that the mixture was red. I'm assuming they use a lot more sand, whereas we use almost pure salt.
Also, my last point is that roads can actually be worse in the south even though we have less snow. Ice on the roads is created when the snow melts and then refreezes. Up north it stays so cold that it doesn't thaw so you don't have that problem. In the south, we have warmer days, so the snow will melt and then freeze at night.
In the north, I've driven across roads of solid white ice without issue. In the south, I've seen roads go from moist to solid sheets of black ice that were impassable.
My teacher told me about this before he left for America and I just don't understand how it works. I'm researching this for our big science project and this website is a big help!
@plaid - I think it's interesting how you become acclimated to the weather wherever you move. It might seem silly, but I am sure there were a few times there when you found yourself becoming a true Texan, yes? I'm sure they were asking themselves "Why is salt used on icy roads" simply because they didn't have enough ice on the roads to deal with. Not looking forward to this winter, however, as it is looking to be a chilly one.
@abiane - That is one of my dad's favorite movies. They actually sell bulk road salt for bigger jobs like driveways and such and that is probably how that guy used to purchase it. Up north, of course, it is more common to see snow plows and trucks come by to salt the roads than other places where it doesn't snow as much. Even though it's not really a funny situation, it's dangerous actually, most people in the south shut down EVERYTHING when it snows only an inch. I lived in Texas for 10 years after living in Maine and it was just absurd.
@ChickenLover - Salt and sand from what I hear are great ice melters. Of course, we can't just go around with hair dryers so we need to find another, more organic, way of dealing with things like that and this is one of the smartest. I didn't know they had actual trucks that came by and did this, although, I suppose in Alaska it would seem necessary. I just remember in that movie Home Alone where the old man used to salt his own sidewalk with a trash can full of salt and a shovel. Anyone else remember that?
When I was younger, we lived in Alaska and Japan. Although I didn't see them actually sprinkle salt on highway roads or anything in Japan, I saw them do it all the time in Alaska. It is a really cool thing how the salt melts the ice and snow away, but it makes the snow really dirty and slushy which can sometimes be worse than what you originally started with.
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