Winter Maintenance Frequently Asked Questions (FAQ)

Understanding Winter Maintenance Procedures

Winter Road Treatments

As in years past, CDOT will utilize a variety of products and techniques for the most effective treatment of snow, slush, ice and black ice on Colorado 's state roadways this winter. Products you will see used in differing combinations include sand, a sand/salt mixture, and various liquid anti-icers and de-icers. The type of storm and temperatures will dictate the products used.

Anti-icers, or preventive winter road treatments, are liquid forms of salt compounds used to prevent the formation or development of bonded snow and ice for easy removal, and are used at the onset of a winter weather storm. They work by lowering the freezing point of water.

De-icers, or reactive winter road treatments, are liquid forms of salt compounds used to break the bond of already existing snow and ice. They dissolve downward and penetrate until they reach the pavement. De-icers melt the ice and snow it may be easily removed by mechanical means such as plows. They are not necessarily intended to clear every bit of ice and snow on the road, though the goal is to keep roads wet.

Both anti-icers and de-icers are winter road treatments that work as freezing-point depressants and are the most desirable and environmentally friendly way to treat winter weather roads.

A variety of factors are taken into account when deciding upon a course of action to treat winter roadways. Product application combinations are chosen after maintenance workers evaluate many factors including air and pavement temperature, humidity levels, dew point temperatures, exposure to solar radiation, type and rate of precipitation, weather forecast, weather radar data, and satellite data. CDOT monitors road conditions using infrared sensors, thermal mapping, and Road Weather Information Systems (RWIS).

Operational treatments are continuously evaluated by CDOT before, during and after a winter weather storm. Road treatments and applications are modified through all phases of a storm based on careful analysis of intensity, duration and type of precipitation.

The Maintenance Decision Support System (MDSS) combines advanced weather prediction, advanced road condition prediction and rules of practice for anti-icing and de-icing to generate road treatment recommendations on a route-by-route basis. The goal of MDSS is to provide more effective use of maintenance resources and increase safety, reliability and mobility on roadways.

This MDSS system allows crews to input real-time conditions, including road and ambient temperature, type of snow removal products being used and the application rate. After comparing the information to 15 weather reports, the system will then provide suggested treatments based on the information and models. The system may tell the operator to re-treat the road at a later time, apply different products at different rates or even to continue current procedures. The suggested treatment can then be followed or the operator can override the system.

CDOT has completed a three-year study into the effects of magnesium chloride on the roadside environment and has found that the product does not significantly harm aquatic or plant life. In fact, the sand/salt mixture used in the past can be more damaging to aquatic life as large amounts of silt are washed into streams. The product does not add air pollutants to the environment and improves air quality by offsetting usage of sanding material. CDOT requires all vendors and suppliers of liquid road treatment products to meet the specifications designated by its research.

As with any form of winter road treatment including sand or salt, liquid anti-icer and de-icer residue should be removed from vehicles with soap and water following winter weather storms. Liquid anti-icers and de-icers are no more damaging to the finish of vehicles than conventional sodium chloride-based products and will wash away with a commercial car wash cleaning. Unlike sand/salt mixtures, the liquids will not damage your car's paint job or windshield.

Colorado utilities report that mist from liquid road treatments, which become airborne due to contact with fast-moving vehicles, can coat insulators that separate electric conductors from the poles that support them. As a result, electricity may jump from the wires to the poles, causing electrical outages. Utility companies across the state perform maintenance to remove the coatings from their equipment to reduce the risk of outages.

There are numerous benefits to using liquid anti-icer and de-icer techniques. Advantages of these solutions on roadways at higher elevations include reduction in the use of salt and sand mixtures and improvement of road conditions during storms beyond what is possible by the use of sand and salt mixtures alone.

Since CDOT began using these products, they have reduced the consumption of sand used for winter road treatment in Colorado by up to 50%. This results in cleaner air and vastly reduced PM10 (particulate matter contributing to Colorado 's “brown cloud” effect).

Liquid anti-icers and de-icers have less negative impact on highway bridge decks, trees and vegetation, and water supply than any other method of winter road treatment utilized in the past. Liquid anti-icers and de-icers are the best products available for preserving the environment.

Since increasing use of liquid anti-icing and de-icing products, there has been a significant reduction in the number of days that state highways are closed due to inclement weather.

Liquid anti-icing and de-icing technology has resulted in cost savings for the state, taxpayers, consumers and corporations. Money has been saved due to energy savings in fuel, reduced wage loss due to tardiness and absenteeism, and reduced production and delivery losses. This technology also helps cut down on windshield claims and paint damage which help save Coloradoans money on auto insurance costs. But more importantly, lives have been saved by reduced accidents and reduced response time to medical emergency.

Snow Removal

During winter, CDOT will have approximately 1,800 trained maintenance personnel working to clear Colorado 's highways and roadways of ice, slush and snow. These fleets will include a variety of winter maintenance vehicles including trucks that spray liquid deicer, trucks that spread sand and snowplows.

CDOT is responsible for maintaining and plowing all Interstates and US highways as well as most state highways. In some cases where a state highway runs through the jurisdiction of a major city, the city will take on maintenance and plowing operations.

CDOT is responsible for snow removal for approximately 23,000 lane miles of roadway. With about 950 trucks, the average time to complete a snow route is approximately 2-3 hours, but some can be as long as 4 hours, especially in urban areas where traffic volumes are much higher. There is also the amount of time needed to load and unload the truck with deicing materials.

During some winter storms, it seems like the Department does a good job, but during other storms it seems that they aren't doing a very good job. Why the difference in performance?

One of the biggest factors that determine our performance is the type of storm and temperatures. Storms with low temperatures can be difficult because deicing chemicals become less effective at the lower temperatures. Storms with high winds also are a challenge because the snow quickly blows back onto the roadway after the plows pass. There are many combinations of winter storms that can hit Colorado during the winter and each pose unique problems to snowplow operators.

CDOT has approximately 950 pieces of snow removal equipment statewide including plows, loaders, snow blowers and motor graders.

During a storm, CDOT maintenance crews work 12-hour shifts and will continue to do so until all the highways are clear of snow and ice.  On highways that have less than 1,000 annual average daily traffic counts, snow removal operations will be limited.

Air temperature is not usually a good indicator of what the roadway surface temperature actually is. During the fall, the pavement is often kept warmer than the surrounding air because of the warm soil. During the spring, the reverse may be true; the pavement temperatures can be colder than the air because the soil is still frozen from the long winter temperatures. The sun also has a strong influence on the pavement temperatures that will help heat the pavement and help the melting process. The difference between air and pavement temperatures can often differ by as much as 20 degrees Fahrenheit.

In the Denver metro area, crews often plow in tandem in order to pull snow and ice away from areas such as walls and medians where drainage is poor. This helps prevent the freeze/thaw cycle that contributes to ice in the driving lanes. Crews make every attempt to accomplish this during low traffic conditions in daylight or near dawn to increase the effectiveness of the de-icing products.

The sanders and liquid systems now in CDOT snow plows are generally controlled by computer/ground speed sensors. The driver usually doesn’t have a lever in the cab anymore to apply material manually. They do have a blast button for intersections, bridges, and icy areas but the computer handles the routine application. Therefore, it is important that you give the plows room and do not follow too closely.

Road Conditions

In making winter road conditions safer, the application of anti-icing and de-icing materials can create some road conditions that require particular attention on the part of motorists. Because liquid road treatments lower the freezing point of moisture on the road, travelers should be prepared for wet conditions. CDOT recommends that motorists carry plenty of windshield wiper fluid in order to clear away any backsplash from the roadway. Additionally, CDOT reminds all drivers to obey posted speed limits with extra care on wet roads and to observe speed advisory plaques posted on curve warning signs. In fact, even the posted speed limit usually is too fast during adverse weather conditions. When liquid anti-icers and de-icers are applied, the road will be wet. Remember, that when a highway is wet for any reason, traction is reduced and the chance of hydroplaning increases.

For information on state highway conditions, you can visit This includes weather-related information, current travel alerts (like chain laws in effect and passes closed), and current traffic conditions. You can also call 511 or CDOT's hotline at (303) 639-1111 in the Denver area or (877) 315-7623 toll-free statewide.

CDOT's Traffic Operations Center is responsible for updating all road condition information provided by CDOT. Updates are made as new data is received from the field or detected by other devices. Because of the large number of highway miles, time may have lapsed between observations. Information is provided from CDOT maintenance employees, law enforcement agencies and weather stations. Since conditions in Colorado can change rapidly, it can sometimes be difficult to provide precise road condition information so it is important for motorists to always be prepared.

Potholes form with the expansion and contraction of water after it has entered into the subsurface of the pavement. When water freezes, it expands, taking up more space under the paving, which then causes cracking. As temperatures increase, the water then thaws, leaving gaps or voids in the subsurface of the pavement. The voids allow for more water to enter under the pavement, creating a vicious freeze/thaw effect, which eventually weakens the pavement. As the weight of cars and trucks pass over the weak spot in the road, pieces of the roadway material weakened by the freezing and thawing effect get displaced or broken down from the weight, creating the pothole.

This process often takes place in the spring as moisture is often trapped in the pavement following the winter or even new storms and temperatures fluctuate from day to night, freezing and thawing the water.

When it comes to repairing potholes, CDOT crews will first focus on those that are causes a safety hazard as well as those on highly traveled roadways. Keeping up with the repairs can often be challenging, especially following large snowstorms such as the blizzards of 2007. In fact, last year, CDOT crews in the Denver metro area repaired near 153,000 potholes.

CDOT has over 55 specialized weather reporting stations that collect road surface information and atmospheric information that reflects conditions on the roadway. The systems measure air, relative humidity, wind speed and direction and precipitation. These weather stations not only help keep CDOT personnel informed of current conditions, but the traveling public.