Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux SECURITY & ADHERENCE TESTING Joël Foucard

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENT ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux PARAMETERS : ROADS CHARACTERISTICS Microtexture : 0,1µm to 10µm height Macrotexture : 10µm to 1mm height

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux  Sand Depth (mm) : mean texture depth Direct measurement : from diameter of sand mark ROADS CHARACTERISTICS MACROTEXTURE : Indirect measurment : computation from laser texture measurement

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROADS CHARACTERISTICS MICROTEXTURE :  SCRIM vehicle : transversal friction coefficient (CFT) on wet road with a motorcycle tire at 20 deg angle

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROADS CHARACTERISTICS FRENCH ROADS DISTRIBUTION : Microtexture : CFT Macrotexture : Sand Depth  Data from transport department : CFT distribution is confidential : cannot be given with this detail level

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROADS CHARACTERISTICS FRENCH ROADS DISTRIBUTION : Microtexture : CFT Macrotexture : Sand Depth  Data from transportation ministry :

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENT ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS MECHANISMS : Hydro-planningX Visco-planningX IndentationXX AdhesionX  Main mechanisms only : Area1Area2Area3Area4 Water thickness>1mm10 µm<<Indenter height 0 Area 1Area 2Area 3Area 4

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS HYDROPLANNING :  Phenomenon : -Loss of contact due to hydrodynamic effects, dependent on speed, pressure, water height, pattern depth  Key actors : - Tire : - Tread pattern - Pressure map in contact patch - Road : - Macrotexture and banking - Absence of ruts

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS VISCOPLANNING : - Squeezing of water between a flat surface and rubber due to water viscosity, as soon as the layer thickness is < 10 µm - Tire : - Eliminate water - Create high local pressure - Road : - Microtexture to puncture the water film goodBad  Phenomenon :  Key actors : h f : final height h i : initial height S : surface P : pressure  : fluid viscosity

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS INDENTATION : - On the top of any indenter, delay between stresses and strains due to rubber hysteretic losses. - Appears at all scales of indenters sizes and associated excitation frequencies - Tire : - Viscoelastic properties under high frequency (10 4 to 10 7 Hz) and high strain - Road : - Texture on a large band of indenter sizes and associated excitation frequencies  Phenomenon :  Key actors : Rubber Ground

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS BRAKING DISTANCE ON WET ROAD : - Dominant mechanisms under these conditions : -Hydroplanning is neglectable -Viscoplanning is dominant on low-micro & low-macro surfaces. Its impact may be emphasised on dirty/polluted roads -Indentation is dominant on almost all clean roads Visco-planning on clean roads Visco-planning on dirty roads  Conditions : 80 to 10 km/h ; Water thickness = 1 mm ; New tire

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux No µ loss due to Hydro Significant µ loss due to Hydro function of tiresize and wear level ADHERENCE MECHANISMS BRAKING DISTANCE ON WET ROAD :  Max rain intensity (2% of the total rain time) : - Measurement of water height above the indenter summit (PREDIT program)  1mm is a maximum value for a good road. More than 1mm occurs in pools and ruts

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE MECHANISMS BRAKING DISTANCE ON WET ROAD :  Conditions : speed, tread pattern depth, water height  Hydroplanning is a significant mechanism in worn tires braking distance

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENT ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux GLOBAL FIGURES : FRANCE ACCIDENT ANALYSIS - INRETS DATA ON 2001 PERIOD - Focus on fatalities - Total of 7720 people killed Pedestrian10,1% Cyclist3,1% Cyclomotorist5,5% Moto13,1% PC64,7% Trucks (1)1,7% Other1,7% Total100% Highway6,4% Regional roads24,2% Local roads53,8% Other15,6% Urban areas (2)25% country75% (1): Trucks = 5,2% of traffic = 5% of injury accidents = 13% of fatalities (2) : Urban areas : = 1/4 of fatalities = 2/3 of injury accidents WhoWhereNote

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux TYPE OF ACCIDENT : ACCIDENT ANALYSIS Longitudinal loss of control : 32%Lateral loss of control : 55%

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux RAIN CONDITION : Weather conditionFatality % Normal75,4% Rain13,6% Snow-Hail0,9% Fog1,2% Others8,9% ACCIDENT ANALYSIS -Average rain duration in France : 9,3% -Known rain effects : -No pedestrian and few cycles and motorcycles -Sensible reduction of passenger cars traffic  Estimation of specialists : 3 times more accident / km in rain condition than in normal dry condition

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux DAMP ROAD CONDITION : Ground conditionFatality % Dry76% Wet20,6% Deep water0,2% Flooded0 Snow0,5% Ice1,4% Others1,4% ACCIDENT ANALYSIS -Damp surface condition : rain condition + drying time -Depending on sources, damp condition = 25% to 40% As recorded in police report, do not take into account very thin layers of water such as : -Moisture retained by road salt during winter -Morning dew  Generic data files do not allow to estimate the severity of damp condition versus dry condition

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD WEAR : ACCIDENT ANALYSIS  The Accident risk level increases as the µ level decreases µ=0,6  Impact on accidents in wet condition

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD POLLUTION : ACCIDENT ANALYSIS -10 years statistics : rain is more severe in fall than in the rest of the year. -First rain after a long period of dryness is more severe because it makes a viscous mixture with chemicals (gasolin, grease, vegetal origin, …) deposited in the bottom of texture  Viscoplanning is extremely unlikely on clean road but may have a significant action on polluted roads  Impact on accidents in wet condition

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ACCIDENT ANALYSIS CUSTOMER NEED VS AVAILABLE POTENTIAL  A margin is available on dry roads for emergency manoeuvers. But there is no such margin on lowest grip wet roads nor in winter. µ coefficient 1,0 0,8 0,6 0,4 0,2 0 Dry Wet Winter Range of adherence used by customers in normal conditions Range of max potential offered by tire/road New road Worn road Polluted road Snow Ice

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENT ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux MICHELIN TEST TRACKS PASSENGER CAR TRACKS CHARACTERISTICS : Microtexture : CFT Macrotexture : Sand Depth L1 L2 L3L4 T1 T2T3 Longitudinal (braking) -L1 : min. threshold -L2 & L3 : axes of product improvement -L4 : research only Transversal - T1 : circular ring, min. threshold -T2 : circular ring,axis of product improvement -T3 : wet handling track, axis of product improvement  Michelin test requirements adapted to our understanding of customer risks

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROAD CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENT ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE AND SAFETY ADHERENCE PERFORMANCE BUILDING : Pneumatic Brakes + Chassis Electronic Systems Customer Reaction Ground contact Potential Fraction of potential use Braking potential Fraction of potential use Road & Weather conditions X X

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE AND SAFETY ABS IMPACT ON SAFETY :  GM study, SIA Paper N° 98-S Scope : -7 GM vehicles models equipped w / wo ABS -5 states in USA -1 year time period -Main résults on casualty accidents : -No significant impact on overall number -Slight increase on dry road due to speed increase with ABS, increase of accident severity -12% reduction on wet roads -22% reduction of accidents involving pedestrian  Improving braking potential pays more on wet than on dry roads

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ADHERENCE AND SAFETY ESP IMPACT ON SAFETY :  Swedish National Administration, Paper N°261 -Scope : -Sweden MB, BMW, Audi-VW, w/wo ESP. ABS on all vehicles -1 year time period -Main résults on casualty accidents : -22% reduction on overall number -9% reduction on dry roads -31% reduction on wet roads -38% reduction on snow & ice  Improving braking potential pays more on low traction roads than on high traction roads

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROADS CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENTS ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux 2 APPROVED METHODS Method using a standard vehicule : braking distance Method using a trailer : µ(G) curve EVALUATION IN RELATIVE Relative performance basis : comparison to a reference tyre : SRTT E1136 (195/75R14) TRACK GENERAL SPECIFICATION Sand depth : mm BPN : TEST TEMPERATURE Wetted surface temperature within 20°C +/- 15°C Temperature variation during test < 10°C WET GRIP REGULATION

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux Standard model passenger car, 4 wheel ABS braking, suitable to accept a wide variety of tire sizes Static tyre load : from 60% to 90% of the tyre load capacity Measurement of the average deceleration of a vehicle between two given speeds Initial speed : 80 km/h Final speed : 20 km/h Water depth : flooded between 0,5 and 1,5 mm WET GRIP REGULATION VEHICLE METHOD :

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux C1C2….Ck : control tyres x x x x x Reference tyre x x x x x x x WET GRIP REGULATION VEHICULE METHOD : Unique reference tire Use of control tire to deal with tire size differences (Test/Reference) = (Test/Control) x (Control/Reference) Vehicle 1 Vehicle 2

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux WET GRIP REGULATION TRACK SPECIFICATION : Norme wet grip Microtexture : CFT Macrotexture : Sand DepthMicrotexture : BPN 40 to 600,4 to 1,0

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux ROADS CHARACTERISTICS ADHERENCE MECHANISMS ACCIDENTS ANALYSIS MICHELIN TEST TRACKS ADHERENCE AND SAFETY WET GRIP REGULATION EURONCAP ADHERENCE TESTING : MICHELIN STRATEGY

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux EURONCAP  Wet adherence issue The risks from our understanding of EuroNCAP project : TRACK SPECIFICATION Macrotexture (Sand Depth) Microtexture (BPN) Wet grip regulation Stone mastic Asphalt Basalt Excellence area of stiff tread pattern Excellence area of soft tread pattern (like winter tread pattern)  If the surface choice is confirmed (against the pneumatic industry expertise), this could handicap the development of the best solutions for low adherence roads

Michelin proprietary informationMercedes-Michelin meeting, 08 June 2004, Ladoux  The track surface evolution is not compatible with absolute braking distance ranking EURONCAP ABSOLUTE RANKING