Temperature Influence on Skid Resistance Measurement Ed Baran

Temperature Influence on Skid Resistance Measurement Ed Baran Principal Engineer (Pavement Testing) Network Services

Temperature Influence on Skid Resistance Measurement* * Braking Force Coefficient at a slip speed of 60 km/h

Introduction Project Aims • Examine temperature influence on skid resistance • Determine the appropriate reference temperature for use in Queensland • Develop F 60 temperature correction factors

Temperature Effects on Skid Resistance “Increase in temperature reduces skid resistance” What temperature ? • Air, tyre, water and pavement surface temperatures. • Water temperature is not significant. • Tyre temperature is a function of air and surface temperature while, • Other factors (load, tyre pressure & vehicle speed) are controlled by test procedures, • Making surface temperature the biggest contributor to tyre temperature. These two players effectively control the temperature game, during skid testing, at the tyre road interface.

Air – Surface Temperature Relationship Dickinson (1981) Temperature Conditions - Typical Cold Season Days - Canberra

Air – Surface Temperature Relationship Daytime Air vs Surface Temperature Relationship – Brisbane DTMR (1985) Oliver (1980)

Air – Surface Temperature Relationship Summary • Asphalt stores heat • Solar radiation plays a big part • Even under cold conditions, surface temperature is unlikely to fall as low as air temperature

Typical Australian Temperature Correction Procedures Use a reference temperature of • 20 o. C surface temperature or, • 23 o. C ambient air temperature while, • 30 o. C surface temperature is used in Queensland. How appropriate is 30 o. C for QLD ?

Temperature Regimes in Australia (Asphalt) Cumulative Surface Temperature Distributions (% less than) Dickinson (1981)

Temperature Regimes in Australia (Asphalt) Cumulative Surface Temperature Distributions (% greater than) Dickinson (1981)

Temperature Regimes in Australia (Asphalt) Temperature Distributions – Comparison with Darwin and Townsville Dickinson (1981)

Temperature Regimes in Australia Annual Average Daily Solar Exposure

Temperature Regimes in Australia (Seals) Asphalt vs Spray Seal (Sydney) Asphalt vs Spray Seal (Perth) Dickinson (1981)

Temperature Regimes in Brisbane (Asphalt vs Concrete) Temperature Conditions - Typical Hot Season Day – Brisbane DTMR (2010)

Surface Temperature – F 60 Relationship Field Trial Nudgee Beach Road Test Site

Surface Temperature – F 60 Relationship F 60 vs Temperature Results Field Trial

Surface Temperature – F 60 Relationship F 60(30) = F 60(t) + 0. 0015(t) – 0. 045 where t = the surface temperature at time of test, F 60(t) = the recorded F 60 at t o. C and F 60(30) = the corrected F 60 value for a 30 o. C reference temperature F 60(35) = F 60(t) + 0. 0015(t) – 0. 0525

Comparison of Temperature Correction Relationships

Conclusions • There is no unique relationship between air and surface temperature. • The reference temperature of 30 o. C is appropriate for the south east and coastal strip of Queensland. • For the north west of the state, the reference temperature should be raised to 35 o. C. • There is minimal difference in surface temperature between asphalt, concrete and seals. • The developed temperature correction relationship can apply to any skid testers that operate at approximately 60 km/h slip speeds and use the ASTM E-1551 standard tyre.