Is there a tire friction variation in cooler temperatures?

Topics related to collision & Trajectory analysis formerly on our 'Registrants only' area however which we get asked about frequently so believe shoud be in the open forum too
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brian
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Joined: Tue Jul 14, 2009 10:52 am

Is there a tire friction variation in cooler temperatures?

Post by brian » Fri Oct 23, 2009 1:28 pm

Q: Is there a tire friction variation in cooler temperatures?
A: Studies have demonstrated that the coefficient of friction can vary with the temperature with the lowest values at or around freezing. See
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Other items which may occur in winter driving conditions are “Black ice” and “wet/icy roadway conditions”. However these conditions still provide friction. The average coefficient of friction for “black ice” is approximately 0.2 to 0.4. The average coefficient of friction for wet and glare ice is approximately 0.2 to 0.6 [1,2,3]. The average coefficient of friction for areas of the roadway which did not have water/ice accumulation was approximately between 0.40 to 0.70. A vehicle passing over a wet/icy area and/or “black ice” would react to the change in friction properties only if the vehicle were either braking or steering in such a manner that the vehicle required friction greater than the 0.2 to 0.4 range.
REFERENCES
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snowicecoeff.gif
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brian
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Re: Is there a tire friction variation in cooler temperatures?

Post by brian » Mon Nov 09, 2009 3:40 pm

The Northwestern Crash Reconstruction Book 1990 edition contained the friction value tables (see below).
There are values for ice and snow which have their origins from the 1940 Book edition (see publication history below). There is a 2010 version of the Northwestern Crash Reconstruction Book coming out in January 2010 and we will report what changes, if any, to the friction table are included.
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Editions History:
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brian
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Re: Is there a tire friction variation in cooler temperatures?

Post by brian » Tue Oct 26, 2010 3:41 pm

Q: Why does it 'feel' more slippery when walking in an area then tire friction measurements may indicate?
A: Well first, temperature changes? and some other items on the topic of walking v driving on an icy/snowy surface:
  • 1) Footwear is not the same as tires both in material and pressure per square inch. This may be part of the issues.
  • 2) You normally walk one foot at a time, your vehicle 'walks' with 4 tires (unless you are on a motorcycle, nuther issue there)
  • 3) Where you walk..are you walking in the tire track/travel area? or on the virginal shoulder, sidewalk, etc?
I also found a report on the web: Assessing slip resistance of wintery walkways with a novel portable slipmeter
which includes some considerations for 'walking' friction.
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MSI
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Re: Is there a tire friction variation in cooler temperatures?

Post by MSI » Wed Jan 13, 2016 8:28 pm

In an earlier post we mentioned we would include any changes to the Northwestern Table of friction coeffiecients;
The 2010 version of the Northwestern Traffic Crash Reconstruction, 2nd Edition book no longer includes a table and includes discussion, portions of which are as follows:
from p 142, Table of Coefficients of Friction
  • Northwestern University Center for Public Safety (formerly Northwestern University Traffic Institute) has provided tables for friction coefficients. The first book (ref 2) (1942) on collision investigation from Northwestern gave approximate friction coefficients for best, average, and wet concrete. Other friction coefficients were suggested as approximate values for packed snow and glare ice. This book was not authored by J. Stannard Baker.

    The first book by Baker was published in 1953, which had a more extensive table of suggested friction coefficients for many surface types. Some changes took place for suggested friction coefficients over subsequent Northwestern books (refs 4 • 5 • 6 • 7 ) on collision investigation and reconstruction.

    Over the years, there have been publications that suggest that the friction coefficient tables given in the 1990 Northwestern reconstruction book7 were valid ranges of expected friction coefficients. Others have been highly critical of the values given in the Northwestern friction tables.

    The values given in a table are clearly not case specific. Each collision case must be evaluated on its own merits. Ideally test skids should be conducted at the collision site shortly after the incident. If icy or snowy conditions are present, the friction values can quickly change. A range of friction coefficients from a table does not mean that the middle value is the average.
    • For new or traveled, clean, dry surfaces such as asphalt or Portland cement concrete that are not traffic polished, you normally expect to have friction coefficients that range from 0.65 to 0.90 for passenger cars or light pickups.
    • Experience suggests that friction coefficients are often not less than 0. 70 and not much greater than 0.85 for clean, dry asphalt and Portland cement concrete pavements that are not traffic polished.
    • Clearly, you can have many exceptions.
    • Moisture on a road surface is probably the most significant contributor to a decrease in friction coefficient.
    • A wet road above freezing temperatures can give friction coefficients that drop by half of what you might expect for the surface when it is dry.
    • For winter conditions with ice and snow, expect to get a variation in friction coefficients. Hunter did friction coefficient tests in the state of Washington over five years with non-ABS vehicles. He categorized the surfaces as several distinct types (frost, heavy frost, tracked snow, untracked snow, snow and ice, black ice, sunny ice, wet ice, and glare ice). For his various winter condition surfaces, the average friction coefficients were as low as 0.19 and as high as 0.63.
    • Martin and Schaefer summarized ranges of friction coefficients for 20 winter road surfaces. Their friction coefficients were as low as 0.054 to as high as 0.72. Eddie31 conducted friction tests on ice and snow and had values as low as 0.10 to a high of 0.33. He concluded that temperature was the most important factor when friction coefficients were determined.
The references listed are as follows:
  • 2. Northwestern University Traffic Institute, Accident Investigation Manual. Northwestern University Traffic Institute, 1942, Revised 1946
  • 3. Baker, J. Stannard, Traffic Accident Investigator's Manual for Police. Northwestern University Traffic Institute, 1953
  • 4. Baker, J. Stannard, Traffic Accident 177 Investigator's Manual for Police. Northwestern University Traffic Institute, 1957
  • 5. Baker, J. Stannard, Traffic Accident Investigator's Manual for Police. Northwestern University Traffic Institute, 1963
  • 6. Baker, J. Stannard, Traffic Accident Investigation Manual. Northwestern University Traffic Institute, 1975
  • 7. Fricke, Lynn B., Traffic Accident Reconstruction, Northwestern University Traffic Institute, 1990
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