High Insert speed the title friction of your of thin surface presentation course here systems Alan Presented Dunford by Name Here 21 Job st May Title 2014 - Date
High speed friction measurement Pavement Friction Tester Locked wheel Spot measurements Range of speeds Research tool rather than routine monitoring
High speed friction measurement PFT measurements 120 100 Locked-wheel Fn 80 60 40 20 0 0 20 40 60 80 100 120 Speed / km/h Example on A5 Gibbet Hill, Lane 1, 10mm section (August 09)
Theory texture scales Two scales of texture Macrotexture / texture depth Macro Microtexture Micro
Theory texture and skid resistance Friction Number 80 60 40 20 Low microtexture, high macrotexture High microtexture, low macrotexture 0 0 20 40 60 80 100 120 Speed / km/h
Theory texture and skid resistance Friction Number 80 60 40 20 Low microtexture, high macrotexture High microtexture, low macrotexture 0 0 20 40 60 80 100 120 Speed / km/h
Theory texture and skid resistance Friction Number 80 60 40 20 Low microtexture, high macrotexture High microtexture, low macrotexture 0 0 20 40 60 80 100 120 Speed / km/h Measure low speed friction with SCRIM (or GripTester)
Theory texture and skid resistance Friction Number 80 60 40 20 Low microtexture, high macrotexture High microtexture, low macrotexture 0 0 20 40 60 80 100 120 Speed / km/h High speed friction not routinely measured Use texture as a surrogate
High speed friction and texture Texture, friction and speed TRL367 120 Open symbols represent Fn values at 20km/h Filled symbols represent Fn values at 100 km/h HRA/SD Locked-wheel Fn at 20 or 100 km/h 100 80 60 40 20 SMA/TS PA BC/GC/TC 0 0 0.5 1 1.5 2 2.5 SMTD (mm) Locked wheel friction against texture depth. Data from all eqm visits to sites.
High speed friction and low texture Collaborative programme 2008 2011 Thin surface course systems with different coarse aggregate - 0/14 mm - 0/10 mm - 0/6 mm
High speed friction and low texture 0/14mm materials broadly typical of traditional pattern 120 Open symbols represent Fn values at 20km/h Filled symbols represent Fn values at 100 km/h 6mm 10mm Locked-wheel Fn at 20 or 100 km/h 100 80 60 40 20 14mm 0 0 0.5 1 1.5 2 2.5 SMTD (mm) Locked wheel friction against texture depth. Data from all eqm visits to sites.
High speed friction and low texture 0/10mm materials broadly similar to traditional pattern 120 Open symbols represent Fn values at 20km/h Filled symbols represent Fn values at 100 km/h 6mm 10mm Locked-wheel Fn at 20 or 100 km/h 100 80 60 40 20 14mm 0 0 0.5 1 1.5 2 2.5 SMTD (mm) Locked wheel friction against texture depth. Data from all eqm visits to sites.
High speed friction and low texture 0/6mm materials performed better than expected at high speeds 120 Open symbols represent Fn values at 20km/h Filled symbols represent Fn values at 100 km/h 6mm 10mm Locked-wheel Fn at 20 or 100 km/h 100 80 60 40 20 14mm 0 0 0.5 1 1.5 2 2.5 SMTD (mm) Locked wheel friction against texture depth. Data from all eqm visits to sites.
Texture as a surrogate for high speed friction? There is no obvious explanation for the uncharacteristic behaviour of 0/6 mm materials - SMTD (or any) texture measurement technique may not adequately characterise the road surface - Smaller-sized particles lead to a different pressure distribution in the contact patch, also affecting the way in which the tyre and road interact - Different contact areas or pressure distributions affect the polishing mechanism and the equilibrium skid resistance developed
Texture as a surrogate for high speed friction? Texture depth on 0/6mm surfacings lower than normally accepted but good performance at high speed So IAN 154/12 relaxes texture requirements for hot applied cl.942 thin surface course systems - 0.9 mm MTD initial, 0.7mm MTD retained With an additional requirement for verification of high speed friction performance So need to develop a high speed friction criterion In principle, applicable to any surfacing
High speed friction criterion
High speed friction criterion
High speed friction criterion
High speed friction criterion
High speed friction criterion
High speed friction criterion Naughty corner
High speed friction criterion
High speed friction criterion
High speed friction criterion Additional requirement for standard deviation between results to ensure consistent surface Peak friction criterion also suggested, but needs development A surface not meeting the criterion should be investigated In principle, any low textured surface could be permitted if it passes the high speed friction criterion
Thank you High speed friction of thin surface course systems Alan Dunford 21 st May 2014 adunford@trl.co.uk
Thank you High speed friction of thin surface course systems Alan Dunford 21 st May 2014 adunford@trl.co.uk
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