Is dynamic spreading possible using only pavement temperature information?

Dynamic spreading is an advanced winter road maintenance approach that adjusts de-icing material application rates based on real-time road condition data. The question of whether pavement temperature information is enough comes up frequently when discussing dynamic spreading with winter road maintenance teams and spreader manufacturers. Why? Because pavement temperature sensors are widely used in spreader trucks. They provide real-time information to the driver, helping to ensure efficient and effective treatment.  

What pavement temperature tells us

Pavement temperatures can vary significantly across a road network, even across a single route. There are many reasons for this — traffic volume, pavement type, exposure to sun radiation, wind and elevation to name a few. As a rule of thumb, cooler pavement temperatures require more treatment materials.

Pavement temperature information can be used for several purposes:

• Deciding when not to spread: If pavement temperature is warm enough (say 37 °F/3 °C or higher), you don’t need to spread because the road won’t freeze even if it’s wet.
• Choosing the right treatment material: The effectiveness of treatment materials like salt or brine depends on pavement temperature. In one example, rock salt (sodium chloride) only works down to pavement temperatures of about 15 °F(-9 °C).

But can you fully automate spreading and dynamically change the application rate based on pavement temperature information alone?

Let’s investigate.

Determining the right amount of treatment material

The main purpose of using treatment materials is to prevent any decontaminate from bonding to the road surface. This allows plowing operations to be most effective.  

How much material is enough? That is the ultimate question. While pavement temperature is important in many ways, that information alone does not provide sufficient information to determine the optimal spreading rate. There are several reasons for this.

The best way to explore this is to look at some practical examples:

• A road could be 28°F (-2°C) but completely dry. Spreading salt would be a waste of time, money, and resources.
• Another road could be 34°F (1°C) but covered in a thin, dangerous layer of black ice due to refreezing. Without addressing that, accidents are almost inevitable.
• Most importantly: A road could have snow/water/ice accumulation, but how much? 0.1 mm? 1 mm? 10 mm? Pavement temperature offers no insight, making it difficult to determine the appropriate amount of salt to spread.

Finding the ideal combination of road weather data

To automatically adjust application rates based on road conditions, you would also need to know how much contaminant is on the road surface at any given moment (layer thickness) — and ideally combine this information with pavement temperature data.  

Of course, layer thickness is not the only information that is helpful. Especially in the U.S., many agencies have used grip information (a simple numerical indicator of how slippery the road is) to adjust spreading rates. This makes sense since grip includes layer thickness information indirectly: The lower the grip on a road, the thicker contaminant layer there typically is and the more treatment it needs.

Filling the road weather gaps with MD30

All of this begs the question: How can you get pavement temperature, layer thickness, and grip data across your road network? This type of information has been available for a few years now, thanks to Vaisala MD30 Mobile Detector.  

MD30 attached to a spreader truck reliably captures critical road state information from every inch of the road network, including pavement and air temperature, layer thickness of water, ice, and snow, grip and more. It can communicate directly with the spreader control system to automatically adjust the application rate according to road conditions as well as the individual policies set up by each agency.

On the road to dynamic spreading

Dynamic spreading uses vehicle-mounted sensors and computerized dispensing systems to automatically adjust the amount of treatment materials based on real-time road conditions.  

We’re seeing a lot of interest around dynamic spreading integrated with MD30 with outstanding results — reducing treatment material usage by 30-55%. Lowering treatment material use through dynamic spreading can dramatically save costs and reduce environmental impacts while still fulfilling the promise of maintaining safe driving conditions.

All in all, pavement temperature information is useful in many ways but is not sufficient to determine the right spreading rate. However, when combined with layer thickness or grip information it can be used for effective dynamic spreading.  

Check out this infographic for a quick look: 7 reasons Mobile Detector MD30 is the industry leader for dynamic spreading systems