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Low Salt Design strategy: Use the sun

This section of the manual is currently under construction.

Pavement recovery is fastest when pavement is in the sun, ice and snow on shaded surfaces are slower to melt. Consider the areas of greatest need for pavement friction (i.e., front steps, braking zones) and optimize them to receive winter sun. Trees, fences, and buildings are all items to consider in neighboring infrastructure and in proposed design.

Illustration of shade and sun on paved surfaces. Take advantage of the sun when possible, to speed pavement recovery from snowfall meltwater sprawl.

Heat on saltable surfaces speeds up pavement recovery. 

Applicability

The Use the Sun strategy should be considered for critical areas such as building entrances, braking zones, and any area where winter pavement friction is critical.

To take advantage of the sun, consider:

  • Building placement/rotation
  • Other structure placement (i.e., noise walls, fences)
  • Vegetation selection and placement
  • Vegetation management  

Benefits and Limitations

Making use of the sun to speed up pavement recovery can be free or can be expensive. Incorporating this design consideration from the start of your project, will make it easier to capitalize on this free element in design.

Design Criteria and Considerations

Put the sun into your CAD system. 

  • Evaluate the angle of the sun on the shortest day of the year; identify the orientation of the sun and hours of sunlight. It will remind you to take advantage of this free resource for melting snow and speeding up pavement recovery.

Shaded areas can be identified using sun analysis software such as Autodesk Forma. Try and optimize the location of critical areas such as braking zone, front doors, hills, sharp curves, crosswalks, high traffic areas to take advantage of sunlit areas (shown in yellow in the figure below). Using the sun is free and one of several strategies to speed up winter pavement recovery.

Example of sunlight analysis, dark color represents persistent winter shade. Image courtesy of Bolton & Menk
  • Albedo is a measurement of how much light a surface reflects or absorbs. Dark surfaces, such as asphalt, have a low albedo leading to a warming effect while white surfaces such as snow or concrete have a higher albedo. 

Retrofit suitability

High: Vegetation management via removal of trees and replacement with shorter vegetation or replacing coniferous trees with deciduous trees is an easily implemented retrofit opportunity to reduce winter shade.

Low: Rotate building, remove adjacent property features casting shade.

Permits and regulations

Some cities have ordinances that restrict tree removal. Some urban designs require shade cast analysis.

Potential conflicts

Climate change: If warming up winter pavement would contribute to climate change, how does that impact compare to the extra danger for the traveling public, and salt loading on a colder pavement?

Research needed

How many hours of sunlight exposure per day are needed to improve winter performance? 

What is the optimal air and/or pavement temperature required to increase performance (based on pavement type, and on pavement with a layer of residual snow).

References and additional resources