Winter Traction – Why Small Rocks, Instead of Sand

Home owners can treat icy sidewalks with sand, but on a slippery highway, whipping winds and passing trucks can blow away light material within minutes.

Instead, when there’s a need for extra traction, our maintenance contractors often rely on a carefully prepared mixture of gravel and crushed stone. The industry term for it is “winter abrasive.” The particles in this mix need to be heavy enough to stay on the road in a wind, large enough not to vanish under new snow or freezing rain, and yet small enough to keep the frustrating windshield chips and paint dings to a minimum.

The right balance between too light and too heavy depends on the type of highway. On main provincial highways, no piece of winter abrasive is allowed to be over 9.5 mm in diameter. That’s smaller than a Cheerio. Very little of the mix is allowed to be even that big, with most of the material falling between 2.36 mm and 4.35 mm in size. (Less-travelled paved highways use a larger mix with a maximum diameter of 12.5 mm.)

How do our contractors make sure that they’re meeting these standards? Many filter their supply of gravel and stone by running it through a series of increasingly fine screens. Others use crushers that grind the material down to the proper size.

Now, you may be saying, this is fine, but what about the time a whopper of a rock cracked my windshield? That was no Cheerio! This has happened to us too, and it can be annoyance or a shock. However, screened winter abrasives aren’t the only rocks on the road. Rocks get washed from the roadside onto the highway, fall from trucks, or get knocked onto the highway by wheels grazing unpaved shoulders.

Your best protection is to keep your distance from other drivers, and if you do get a windshield chip, have it fixed right away.

Did you know?

  • If a rock strikes your windshield, the potential damage has more to do with the rock’s impact velocity than its size. An increase in impact velocity from 80 km/h to 110 km/h will almost double the impact energy and the probability of windshield damage. So to protect your vehicle: slow down and keep your distance!
  • On flat, straight highway sections, maintenance trucks may briefly stop applying abrasives to avoid spraying vehicles passing in the other direction. However, they can’t do this on hills and corners — these crucial areas must be treated.
  • Maintenance crews sometimes wet winter abrasives with a liquid brine to help it penetrate compact ice and stick to the road.


  • Avoid passing a truck applying winter abrasives if you can. Staying back will protect your vehicle from flying winter abrasive, and you’ll be safer driving on the treated road. If you do need to pass, patience will pay off. Our contractors regularly pull over to let traffic pass when it’s safe to do so.

Page 1 of 55 comments on “Winter Traction – Why Small Rocks, Instead of Sand”

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  1. So what about when a sand truck coming towards you and you slow your vehicle to 60km on the highway and the sand truck operator does not turn his spreader off and completely destroys your paint job? My vehicle requires a new windshield, and repainting on my hood, roof, side front panels all the way back to my gas tank. Is there no procedure the driver must follow? Are us northern community drivers supposed to pay for their negligence?

  2. Complete disaster yesterday I’m so pissed furious.
    One trip to kamloops and back from Vancouver
    My brand new Mercedes sprinter has well over 200 paint chips
    And three major chips on the window.
    It will require a complete repaint which means it will no longer be a factory paint job
    Plus the inconvenience.
    This gravel on the highway is insane
    As the the snow melted yesterday on the highway between Hope and Merritt you can see from the traffic large major pools of gravel that has been comsolidated by the traffic and tremendous water from melting snow.
    One semi after another were ripping through the pools of water and gravel and launching it every wear if I took a pail of gravel and through it at the front of my van about a thousand times that was my trip yesterday.
    I seriously would like to kick the guy in the nuts who thinks placing tons of gravel on the highway is a good idea
    I paid 70,000 plus tax for my van and it is destroyed with only 20,000 k
    Seriously like explain to me why my van should be destroyed.
    Absolute stupidity

    • Hello Stephane,

      Thank you for letting us know. We are forwarding your comment to the district office for follow up.

    • Hi Stephane,

      We want to assure you that, your concern about the damage to windshields and paint that occur as a result of winter abrasives and ponding water are being heard. Below is some information from the district office for you.

      In response to your inquiry about the size of the winter abrasives, the ministry currently uses 12.5 mm winter abrasives, we use this size because it stays on the road; smaller sizes tends to get blown off, especially when there is a lot heavy truck traffic like the Coquihalla gets. This size also provides a higher level of safety in the traction restoration of slippery surfaces on the steep challenges these routes present. The ministry works closely with its maintenance contractors to insure the standard specification for size is not exceeded. This year we have performed audits on the contractors stockpiles to ensure our stringent standards are being met.

      You might know that, since February 10th, the Coquihalla has seen upwards of 3 metres of fallen snow. This recent “pineapple express” has seen soaring day temperatures and heavy rainfall, resulting is areas of ponding water and accumulations of winter aggregates caused by the rapid melt and accompanying rain.

      You’ll be interested to know that the ministry is currently doing a review of the best practices in this area (checking with other jurisdictions about their standards and experience); we are also doing some selected trials ourselves(testing the effectiveness of the smaller abrasives and different application methods) and we hope to be able to have enough information by the end of the winter to be able to determine whether we can alter our specifications without reducing the safety of the travelling public.

      If you have further comments/issues that you would like to share with us , please don’t hesitate to contact our local Operations Manager he can be reached at or by telephone at 250-378-1414. The ministry’s main focus is to provide a safe, reliable, highway system for the travelling public and feedback from people such as yourself is an important part of the process. Thank you.

  3. The chemicals you are using on the highways are causing serious paint pitting in vehicles. You must stop using these chemicals. We cannot afford to have our vehicle re-painted every year!

    • Hi Kathleen,

      Thanks for letting us know of your concern. Is there a specific area that you travel, so we can follow up with the maintenance contractor?

  4. Do you realise that the size of this material is causing massive damage’s to cars that travel the highways and side street’s in BC.
    From most common damage is windscreen and paint damage.
    My car has been damage by your product and ICBC will not cover this damage I was lucky and my private portion covered me but for the most part people’s insurance does not cover damages caused by your product due to the size used.
    This gravel product is like having some one shot at you with a pellet gun or throwing a rock at you at high speed do you not do test on this product before you went and used it???
    Pedestrian’s and motorbike riders are also facing damage’s to their bodies or eyes.
    So at the end of the season do we send our repair bills to the government because as stated ICBC will cover you and thus you have to replace the windscreen and pay your deductible or do you feel this is fare???? And then get a re-spray on the front end of the car due to your product damaging my personal property.
    Most new cars and truck are throwing these stones as they fit between the tires treads and then they dislodge and are catapulted at the car or truck behind them (this is not the fault of the driver in front)some times they fly out the side and hit pedestrian’s.
    Even if cars or trucks are fitted with mud guards it still realises and hits something.
    To call this product SAND is totally incorrect its a small GRAVEL product.
    I would like a response as this is becoming a too common problem on our highways and if the governments own insurance body ICBC will not cover the damages I feel their is a major problem.
    Sincerely ,
    Andrew Crane.

    • Hi Andrew, thanks for your comment.

      You’re correct; we do not use “sand” on B.C. roads. As mentioned above, the maximum allowable size of the abrasive is 12.5 mm, so winter abrasive is much coarser than sand. The fact is, if the winter abrasive is too fine, it simply blows away and creates a safety risk. Therefore, unfortunately, using this kind of winter abrasive is a necessity during the winter to control slippery surfaces and improve safety for the travelling public.

      Material rocks larger than 12.5 mm do sometimes end up on our highways. However, they often come from other sources, such as private haulers or other vehicles that drop larger materials onto the highway after exiting resource or side roads.

      I can tell you that we’re constantly researching to find better methods and new technologies to improve the safety and reliability of our roads during the winter months, while minimizing the potential for vehicle damage. Until we find something better, however, we will continue to use the current size of abrasive to ensure the travelling public has adequate traction during those cold winter days. we’ll still be using this kind of abrasive.

      • I agree with this person very strongly. I live in Grande prairie and we get 80km/hr plus winds sometimes. We barely get abrasives on our roads and when we do its SAND! Guess what it doesn’t go everywhere like you say it does. The roads can be slick yeah for sure but its not that big of a deal. Drive according to the conditions right. I literally just drove through Armstrong an hour ago and at 70 km/hr I had roughly 4 or 5 STONES that are probly the described 12.5 mm size bounce off my windshield and hood, pillars etc. All coming from cars a good distance in front and also from beside me. I now have a rock chip that is spreading in 10 different directions and since my Subaru has wiper defrosters built in this will be a $1000 plus repair! Obviously you guys aren’t going to pay for it so no big deal on your part I guess.

        • It is ridiculous, made approximately four trips to Kamloops with a brand new Cruze, made the mistake is washing it. Counted a dozen chips on the hood, and I tried very hard to not get any if you know what I mean.