Ways Cities Clear Roads of Snow and Ice
Up here in the Great White North, when the snow comes down, the plows come out. Before the snow season starts, city crews are planting tall fluorescent markers at the edges of roads as guides for the plows and to mark fire hydrants for firefighters. As soon as there are ten or more centimetres of snow on the ground, the plowing and salting begins.
The equipment involved is immense. Cities that get real winters maintain a large fleet of snow-clearing vehicles, from tiny Caterpillers and Bobcats to clear the sidewalks, to large customized graders with two large front plows, one slightly behind and to one side of the other, and a third one underneath in the middle. The graders can't quite make it to highway speed, but they come close.
Complementing the plows are the gritters, which spread a sand and salt mix. They look a lot like dump trucks, but underneath they have a scattering device called an impeller that looks a bit like a circular-track sprinkler. Their sand and salt load goes directly out from the hopper to the scattering device and onto the roadway.
In between aregritters which are also fitted with grader-sized snowplows. The plow blades remove the snow in front, and the salt and sand gets spread underneath the truck on the cleared surface.
Cities always start on the major commuting roads. On the major multilane highways, four or five graders will set up in aslant formation, with the one near the centre of the highway in front and each grader to the right a little to the back. That way, each grader catches all the snow from the grader in front and pushes it to the right, until the last grader in the V pushes it off to the right side of the highway.
At the same time, the combination gritter-plows start working on major bus and streetcar routes and main roads, gradually working their way down to the small subdivision roads. During heavy snowfalls, this can mean a few hours wait before the smallest cul-de-sacs get plowed out, even though the snowplow crews are working 24/7. During multiday snowfalls, the cul-de-sacs might get ignored entirely until the snow stops falling.
Of course, when snow is being pushed off to the side of the street, that means the sand/slush/snow mixture is also getting pushed to the side to block your freshly cleaned driveway. If you don't shovel it out right away, it's going to harden into ice. Still, it's a small price to pay for being able to drive on a freshly plowed road.
Meanwhile, the small Bobcats and Caterpillars are doing exactly the same thing along the sidewalks. Their blades are V-shaped, so they cut into the new snow and push it to both sides. Their weight also flattens the remaining snow, so that the sidewalk surface is a layer of hardened snow rather than bare sidewalk.
Downtown, many cities require business owners to clear the sidewalks in front of their businesses. There, you see bare sidewalk.
The railroads have their own special equipment to clear snow off the track. In heavy snowfall areas, locomotives are usually fitted with a snowcatcher as well. It works so well that we've never cancelled a train because of snow. Even during the four-metre snowfall which hit Ottawa a few years back, 75% of the trains ran on time.
When there's warning of a major coming snowfall and the temperature is only a few degrees below freezing, the gritters get out on the major streets ahead of the snow and treat the road surface with brine before the snow falls. This keeps the snow from sticking and even melts some of it right away. They can't use brine in advance when the temperature is too cold. That just makes the ice situation more dangerous.
Cities in the whiter parts of the Great White North can't wait for it to stop snowing before they start plowing out. Just before Christmas, we had over a metre of snow in just a few days. If we waited until it stopped to start plowing, we'd never get anywhere.
Most heavy snow cities also have bylaws against leaving cars parked on the street all night. That's so that they don't get in the way of the plows. Cars which do get in the way of the plows can be towed.
With that amount of snow on the ground, cities also have to remove the snowbanks at the side of the road, so that there's still somewhere to put the snow the rest of the winter. We do it with front end loaders and dump trucks, and cart the snow to holding areas where it sits around until May or June before it finally all melts.
With all this, snow removal budgets are one thing that never faces the budget axe. Canada as a whole spends about $1 billion on snow removal. Even small cities budget half a million dollars or more for snow removal. Toronto tried to cut down the budget one year, but got caught short of equipment when a snowstorm dumped more snow than expected. That never happened again. Toronto learned its lesson, but we still tease Torontonians about the time they had to call the army in to deal with 17 cms of snow.
Finally, at the end of the snow year, the sand sweepers come out and brush away all the leftover grit from the street to the gutters, where the rain washes it away down the storm drains. Everything is left nice and clean, all ready for next winter.
