More complicated than you thought
Winter road maintenance is actually far more complicated than just laying down salt. Each jurisdiction has its own routine of when it plows, and what sort of anti-icing or traction aids it uses. This depends on several factors, including the region’s average winter temperatures, the types of roads (such as city versus rural or highways), the number and type of trucks it has, and its budget.
The most familiar solid ice agent is rock salt, which is sodium chloride. Technically, rock salt doesn’t actually melt the ice. Rather, it lowers the ice’s freezing point—which is normally 0C—so it will melt with the ambient temperature, even though the thermometer has dropped below zero. It’s good to about -20C. Below that, even salted ice will remain frozen.
Pre-wetting and anti-icing
Even before a storm, you’ll often find trucks spreading brine on dry roads – this is known as anti-icing. This liquid salt dries up, leaving a salt residue—it looks like white lines on the asphalt—that helps to prevent ice from bonding to the road once the wet stuff falls out of the sky. This makes it easier for the snow plows to scrape the surface bare.
Some salt trucks carry brine that’s sprayed on the rock salt just before it’s scattered on the road. Known as pre-wetting, this prevents the salt from bouncing too much, and also kick-starts the melting process.
As much as 8 times more expensive
But many areas—we are living in Canada—drop well below the -20C effectiveness of salt, and so they may use other solid or liquid agents, either alone or in combination with salt. These include potassium chloride, calcium chloride, magnesium chloride, urea, and potassium acetate.
The catch with these compounds is that they are all more expensive than rock salt, which is relatively cheap. Potassium acetate is biodegradable and can melt ice when the temperature drops as low as -60C, but it’s as much as eight times more expensive.
Corrosion and run-off are also problematic, since salt can damage concrete and kill vegetation. Some of the more expensive alternatives create less environmental havoc, and are often used in specific areas, such as on bridges or near waterways, where the benefits outweigh the cost.
Sand and… beet juice!
A few regions, including Toronto, even use beet juice as a pre-wetting agent in certain situations. It’s the residue left over when sugar beets are refined into sugar, and it’s effective to -32C.
It’s four times the price of salt, but it can reduce salt use by more than 60 per cent, and it isn’t environmentally harmful in itself.
But of course Canada has areas that get even colder than that, and stay that way throughout the winter. Anti-icing agents do no good, and so trucks dump sand to provide traction for drivers and pedestrians. It’s often mixed with five to 10 per cent salt, known as “pickled sand,” which helps prevent clumping.
It’s far more environmentally friendly than salt or de-icers, even when a little salt is mixed in, but it’s not without its drawbacks.
For one thing, it has to be shovelled or swept away when winter is over. In more moderate areas, where winter temperatures regularly rise above freezing between snowfalls and everything melts, it would have to be reapplied each time, since it’s only effective when it’s sitting on top of the ice. The resulting accumulation can then clog storm drains.
Any savings gained from the lower price of sand would be far exceeded by the cost of getting rid of it in more moderate climates.
Stuck behind? Take a deep breath…
No matter what type of anti-icing or traction agent they’re dumping, all snow plows have one thing in common: no one wants to be stuck behind one. But if you are, then take a deep breath, sit back, and follow it, which is the safest thing to do.
Snow plow operators have limited vision because of the blade, and chances are good they can’t see you if you’re coming up alongside. It’s especially dangerous if you try to weave your way through a “conga line,” which is two or more plows working together to clear all the lanes on the highway.
Drivers who pass on the side that isn’t yet plowed often end up losing control, and hitting the plow or an oncoming driver, or ending up in the ditch. Plow drivers follow a circuit, and eventually, they’re going to turn off and leave the road open for you.
Hey, it’s winter in Canada. It’s all part of the charm.