Snowplows, salt and anti icing: how crews treat winter roads and how to drive near plows
How salt, brine and sand work, when crews use each and how to give plows room
Safety Behind the Wheel Foundation built this guide from Federal Highway Administration (FHWA) road weather guidance and reports, Colorado Department of Transportation (CDOT) snow removal practice, Occupational Safety and Health Administration (OSHA) winter guidance and published research on winter maintenance. Every source is listed at the end.
Why plows, salt and anti icing matter for safety
Snow and ice take away the grip your tires need. The Federal Highway Administration (FHWA) says they reduce pavement friction and make vehicles harder to maneuver, which slows traffic and raises collision risk [1]. On snowy or slushy pavement, average speeds on arterials (major city roads) drop by 30 to 40 percent [1].
This is a national issue. More than 70 percent of roads in the United States lie in snowy regions, and nearly 70 percent of the population lives there [1]. Each year, public agencies at the state and local level spend over $2.3 billion on snow and ice control [1].
Storms raise the odds of a collision. A Canadian study looked at 196 winter storms in one midsized community. Injury collisions rose 66 percent during storms, and noninjury collisions rose 137 percent, compared with dry weather [2]. The increase shrank over the study period. The authors called for more research on which winter safety steps deserve the credit [2].
Winter maintenance treats a storm in three stages: before it starts, while it falls, and after it ends [3]. This article covers what the equipment does, how crews choose treatments, how to drive near plows, and how to choose and care for equipment at home or work. Our guide to driving in snow and ice covers grip, black ice and skids, so this article leaves those skills there.
Plows: what they do and the kinds you will see
A plow does one main job. It pushes snow off the driving surface so your tires can reach pavement. Crews also treat the road with chemicals, and the two steps help each other. One state transportation agency says plowing goes more easily when anti icing and deicers are used together [3].
Maintenance trucks may carry plow blades, tanks for liquid chemicals, spray nozzles and spreaders for solid material [4]. Crews rely most on sand, salt and anti icing chemicals [4].
You may see several kinds of plows:
- Front plow: A blade mounted on the front of a truck. This is the standard plow.
- Wing plow: A second blade that extends to one side. A truck can carry its wing on the left or the right [5].
- Tow plow: A steerable trailer with its own blade, towed by a heavy dual axle plow truck [5].
- Tandem formation: Several plows staggered on a multilane road. Each plow runs behind and to the side of the one ahead, so the group clears every lane in one pass [3].
Crews adjust as a storm changes. Supervisors and drivers may change how much material they spread, and which routes they take, depending on the weather and the state of the road [5]. Some agencies treat snow emergency routes first and spread salt and sand ahead of the snow [5].
Salt, brine and sand: anti icing, deicing and prewetting
Three terms come up often.
- Anti icing is treating pavement before a storm so snow and ice cannot bond to it [3].
- Deicing is treating pavement after snow or ice has bonded. The product dissolves downward until it reaches the pavement and breaks the bond [3].
- Prewetting is wetting granular salt or sand with liquid before it is spread. One city does this to help the material stick to the road [6].
The table below shows how these treatments compare.
Comparison compiled by Safety Behind the Wheel Foundation
Anti icing, deicing and prewetting compared
| Treatment | When and how it is used | Main limit |
|---|---|---|
| Anti icing brine (salt water) | Applied hours before a storm. It dries as white stripes on the road [3]. | Must go down before ice forms, so crews need a good forecast [4] |
| Deicing liquid or granular salt | Used once snow or ice is present. It dissolves downward to the pavement [3]. | Weakens as pavement gets colder [3] |
| Prewetted salt | Granular salt wetted before spreading so it sticks better [6] | Still salt, so it carries the same water and corrosion concerns [3, 10] |
| Sand or sand and salt mix | Used mostly where cold is extreme and traction is needed [3] | Adds grip but must be cleaned up later [12] |
Why pavement temperature matters
Salt works by lowering the freezing point of water. The colder the pavement, the less it can do. One state shows how crews handle this. Its crews use a liquid chloride product when pavement is above 16°F. They use a cold temperature magnesium chloride blend below 16°F. A third liquid product is used when pavement is above minus 4°F [3].
The same agency says crews stop using the anti icer once snow starts to fall or the temperature drops below freezing. They then switch to deicers [3]. Its products all contain salt with added corrosion inhibitors, which are meant to limit damage to vehicles [3].
Crews also get help from software. A maintenance decision support system is a tool built to help managers make road treatment decisions [4].
Spreaders and sprayers: how material gets on the road
A spreader places granular salt or sand on the road. A sprayer does the same job with liquid. Both ride on trucks and trailers. For small jobs, they also come as pickup bed units and push carts.
Rates matter. Too little leaves ice behind. Too much wastes material and sends more chloride into the environment [10]. Crews therefore track what they use. To know how much salt each road receives, agencies equip trucks with location tracking and material monitoring [5]. One state’s truck data records speed, location, plow status and application rates [5].
Not all spraying comes from a truck. Some locations use fixed automated spray systems. Sensors detect ice conditions, and the system sprays anti icing chemicals when set thresholds are met [7].
What the research says about benefits and trade offs
These studies use models and real world data, not controlled trials.
Canadian researchers built a model of snowstorm collisions. In a hypothetical storm, anti icing was linked to 14 percent fewer collisions [8]. Plowing was linked to 33 percent fewer, and doing both to 42 percent fewer [8]. A 2024 study used connected vehicle data, which is information sent from cars. It found that winter maintenance cut crash related traffic delays by about 60 percent [9]. It also cut harsh braking events per crash by about 19 percent [9].
Salt has costs. A research review found that long term winter use of road salt raises chloride levels in rivers and lakes, because chloride reaches groundwater. Chlorides appear to reduce the variety of aquatic plants and animals [10]. In various German cities, sodium chloride is not allowed on separated bike paths because it harms nearby trees [12].
Alternatives are not simple. A lab study tested three deicers sold as “eco friendly” on midge larvae. Two were about as toxic as a traditional chloride salt product, because they also contained chloride salts. A urea based product was about ten times more toxic [11]. A label is not proof, so ask what the product contains.
Sand has its own trade off. The Hamburg cycling study warned that leftover grit on dry pavement can cause serious injuries, so it has to be cleaned up when winter ends [12].
Driving near plows and treatment trucks
Plows are big, slow and busy. They throw snow, slush, sand and debris, and they may stop or turn with little warning. In a survey of 1,043 winter maintenance operators in 29 states, about 75 percent said they at least sometimes drive while fatigued [13]. You cannot see how tired a driver is, so give plows room.
Here is a routine to follow when you see plow lights ahead:
- Ease off the gas early. Plows often travel slower than traffic, and sudden braking on snow is risky.
- Drop back at least three to four car lengths. That keeps sand and deicer off your car and gives you room if the plow stops suddenly [3]. Safety Behind the Wheel Foundation gives every driver the same advice. Add more room on slick roads, and check your state transportation agency for any rule on following distance.
- Stay behind the plow. The lane behind it has just been cleared and treated, so patience is usually safer than passing.
- Never pass on the right, because plows throw snow, slush and loose debris to that side [3]. Never pass plows that run in a line. Blowing snow can hide the road, and snow ridges can form between lanes [3].
- Do not ride beside a plow. A wing blade extends to one side [5], and the driver’s view is limited.
Who is responsible and how to ask for a review
State transportation departments, counties and cities plan, buy and run the equipment for public roads. They also choose where to plow first. Residents should never treat public roads themselves. Report a problem spot to the agency instead.
Agencies set priorities, and your road may wait. In Colorado, the state agency plows state highways with 1,000 or more vehicles a day throughout a storm. On highways with fewer than 1,000 vehicles a day, snow removal is limited to 14 hours, from 5 a.m. to 7 p.m. Exceptions may be made for school bus routes, spots with high collision rates, and hospital or emergency routes [3].
One city ranks arterials first, then collectors, school routes and residential streets. Its goals are to reach bare pavement on major arterials four hours after a storm ends, and on collector roads six hours after. It also aims to reopen sidewalks within a day [6]. Crews return in loops. One state sets a maximum cycle time of 3 hours on state highways and 2.5 hours on interstates [5]. A cycle time is how long a truck takes to finish its route.
Choosing and using treatments for driveways, lots and small fleets
Many buyers need winter road equipment. Drivers keep ice melt and sand. RV owners and rural property owners face long private lanes, gravel pads and farm roads. Fleets treat yards and parking lots. Road agencies buy heavy trucks, sprayers and brine systems.
Small products are sold at auto parts stores, hardware and outdoor stores, and farm and ranch supply stores. Equipment dealers and roadside equipment suppliers sell larger spreaders and plows. Engineering contractors design and install large or fixed systems.
Use the table below to match the treatment to the job.
Comparison compiled by Safety Behind the Wheel Foundation
How to match a winter treatment to the job
| Question | What to check | Why it matters |
|---|---|---|
| What is the surface? | Read the product label for surface warnings (asphalt, concrete, pavers, gravel) | Different surfaces tolerate different products |
| How cold will it get? | Pavement temperature against the product’s working range | Salt weakens as pavement cools [3] |
| What is nearby? | Wells, streams, trees, lawns and pets | Chlorides reach groundwater and streams [10], and salt can harm trees [12] |
| Do I need traction? | Steep or shaded areas | Sand adds grip [3] but must be swept up [12] |
| How big is the area? | Hand spreader, walk behind spreader or truck mounted unit | A spreader that fits the area applies material evenly |
Walkways and lots matter, too. Snow on the ground raised the chance of a pedestrian slip more than threefold in a Finnish study of 16 cities over 14 winters [14]. The Occupational Safety and Health Administration (OSHA) advises clearing snow and ice from walkways and spreading deicer quickly once a storm ends [15]. Plow or shovel first, then treat what is left.
A plow blade on a pickup truck changes how the truck handles. The blade adds weight at the front. Follow the vehicle maker’s rating for the mount and the plow maker’s instructions, and ask a qualified dealer or installer. Never push snow across a public road lane or onto traffic.
Care, storage and common mistakes
Salt is hard on metal. After trips on treated roads, rinse the underside of your vehicle and trailer, including brakes and wiring. Rinse spreaders, too, and store salt dry and covered.
Fleets and employers need a plan. OSHA advises employers to set and enforce driver safety rules. It also advises a maintenance program for every vehicle and piece of powered equipment their workers operate [15]. Plan rest breaks and shift lengths, since fatigue is common among plow drivers [13].
Common mistakes are easy to avoid:
Frequently asked questions
Why is the road still slippery after a plow went by?
A plow removes the snow, but a thin layer of ice can remain. Treatments need time to dissolve ice, and they work more slowly when pavement is very cold [3]. Bridges and shaded spots can also refreeze. Keep your speed down even on a road that looks clear.
What are the white stripes on the road before a storm?
They are usually dried anti icing brine, not paint. Crews apply it hours before a storm so snow and ice cannot bond to the pavement. Once it dries, it shows up as white stripes [3]. You can drive on it normally.
Is it ever safe to pass a snowplow?
Passing a plow carries real risk. Plows throw snow and debris to the right, and a line of plows can blind you with blowing snow and leave ridges between lanes [3]. Many plow drivers also work long, tiring shifts [13]. Staying behind the plow is usually the safer choice.
Does salt work in very cold weather?
Not as well. Agencies change products as pavement temperature falls. One state uses a cold temperature blend below 16°F [3]. For home use, read the label for its working range. Sand can add grip when salt is weak, but it does not melt ice and must be swept up later [12].
Is road salt bad for the environment?
It can be. Long term salt use raises chloride levels in rivers and lakes through groundwater [10]. Agencies track how much material they spread [5]. At home, apply a thin, even layer and keep it away from wells, streams and trees.
How can I get my road treated or plowed sooner?
Find out which agency owns the road. Ask about its priority levels and service goals. Agencies often rank roads by traffic volume, and school and emergency routes may get exceptions [3, 6]. Report icy spots and missed streets through the agency’s reporting channel rather than treating public roads yourself.
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Safety Behind the Wheel Foundation urges drivers to give plows room and stay behind them, and urges property owners to apply winter treatments thinly and only where needed. Plows, salt and anti icing are a team. Plows clear the bulk of the snow, anti icing keeps ice from bonding, and deicers break up what has already stuck. Crews pick products by pavement temperature and track how much they use.
Your part is simple. Give plows room, stay behind them, and never pass on the right. On your own property, choose treatments for the surface, the weather and the environment, apply them thinly, and keep equipment clean and ready. If a road near you stays icy, report the spot and ask the agency how it is prioritized.
Related articles
- Driving in snow and ice: grip, black ice, skids and when to stay home
- Safe following distance: the 3 second rule and when to add more
- Journey management for work drivers: weather, breakdowns and check ins
- Fleet vehicle safety: how to choose, maintain and inspect work vehicles
- Rural road safety: why country roads are deadlier and how to drive them
Sources and further reading
- 1Federal Highway Administration (FHWA), Road Weather Management Program. Snow & Ice. Updated: date not shown on page. Data year: not stated on page (FHWA gives annual figures). ops.fhwa.dot.gov/…/snow_ice.htm
- 2Mills B, Andrey J, Doberstein B, Doherty S, Yessis J. Changing patterns of motor vehicle collision risk during winter storms: A new look at a pervasive problem. Accident Analysis & Prevention, 127:186-197. Published March 2019. Data year: 2002 to 2016 study period as described in the abstract. pubmed.ncbi.nlm.nih.gov/30897524
- 3Colorado Department of Transportation (CDOT). Snow Removal & Safety. Updated September 21, 2023. codot.gov/travel/winter-driving/snowplow-safety
- 4Federal Highway Administration (FHWA), Road Weather Management Program. Decision Support, Control and Treatment. Updated: date not shown on page. ops.fhwa.dot.gov/…/decision.htm
- 5Federal Highway Administration (FHWA). Adaptive Route Optimization (ARO) for Operations: Literature Review, Technology Scan, and Early Adopter Interviews (report FHWA-HOP-21-098). Published October 2022. ops.fhwa.dot.gov/…/fhwahop21098.pdf
- 6Federal Highway Administration (FHWA). Weather-Responsive Management Strategies: The City of Fort Collins, Colorado (report FHWA-HOP-22-057). Publication date not shown in the document. Data year: not stated (current city operations as reported). ops.fhwa.dot.gov/…/fhwahop22057.pdf
- 7DiLorenzo T, Yu X. Use of ice detection sensors for improving winter road safety. Accident Analysis & Prevention, 191:107197. Published July 2023. pubmed.ncbi.nlm.nih.gov/37459791
- 8Abohassan A, El-Basyouny K, Kwon TJ. Exploring the associations between winter maintenance operations, weather variables, surface condition, and road safety: A path analysis approach. Accident Analysis & Prevention, 163:106448. Published October 2021. Data year: not stated in the abstract. pubmed.ncbi.nlm.nih.gov/34717203
- 9Oh M, Dong-O’Brien J. Assessing the safety impacts of winter road maintenance operations using connected vehicle data. Accident Analysis & Prevention, 209:107837. Published November 2024. Data year: not stated in the abstract. pubmed.ncbi.nlm.nih.gov/39550796
- 10Szklarek S, Gorecka A, Wojtal-Frankiewicz A. The effects of road salt on freshwater ecosystems and solutions for mitigating chloride pollution – A review. Science of the Total Environment, 805:150289. Published September 2021. pubmed.ncbi.nlm.nih.gov/34536879
- 11Nutile SA, Solan ME. Toxicity testing of ‘eco-friendly’ de-icing formulations using Chironomus dilutus. Environmental Pollution, 246:408-413. Published December 2018. pubmed.ncbi.nlm.nih.gov/30577009
- 12Lissner S, von Harten M, Francke A, Ruf S, Hagemeister C. Safe cycling in winter: Results of a case study on the role of de-icing in the city of Hamburg, Germany. Journal of Safety Research, 87:244-256. Published October 2023. Data year: not stated in the abstract. pubmed.ncbi.nlm.nih.gov/38081698
- 13Camden MC, Medina-Flintsch A, Hickman JS, Bryce J, Flintsch G, Hanowski RJ. Prevalence of operator fatigue in winter maintenance operations. Accident Analysis & Prevention, 126:47-53. Published February 2018. Data year: not stated in the abstract (survey of operators in 29 states). pubmed.ncbi.nlm.nih.gov/29397874
- 14Hippi M, Kangas M. Impact of Weather on Pedestrians’ Slip Risk. International Journal of Environmental Research and Public Health, 19(5):3007. Published March 2022. Data year: 14 winters in 16 Finnish cities (years not stated in the abstract). pubmed.ncbi.nlm.nih.gov/35270700
- 15Occupational Safety and Health Administration (OSHA). Winter Weather: Hazards/Precautions. Updated: date not shown on page. osha.gov/winter-weather/hazards
This article reflects the safety priorities of winter road maintenance and safe driving near snowplows. It is general education, not legal, medical, insurance or financial advice. Agency practices and product rules change, so verify details with official sources. For your own situation, contact your state or local transportation department or public works office about public roads, and ask a qualified equipment dealer, installer or contractor about equipment for your property. Reviewed October 2026.
Cite this article: Safety Behind the Wheel Foundation. “Snowplows, salt and anti icing: how crews treat winter roads and how to drive near plows.” drivewithcare.org, https://drivewithcare.org/snowplows-salt-spreaders-anti-icing/. Reviewed October 2026.
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