Friction measurement methods and the correlation between road - VTI

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Relative risk16141210864200 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95Skid-resistanceRelative riskFigure 4.4 Relative rate of a surface being a skidding-accident site for differentvalues of skid-resistance.The rate becomes measurable below 65 and increases sharply below values of50 to 55. The form of the curve suggests that values below 55 are likely to beaccepted only on roads with easy traffic conditions, and values below 45 probablyindicate potentially slippery conditions whatever the road layout and trafficconditions.Schulze, Gerbaldi and Chavet [49] account for analyses from the Netherlands,the Federal Republic of Germany, and France. In the Netherlands all accidents onstate roads during two years, 1965 and 1966, have been used in a regressionanalysis. The accident rate was derived from the number of accidents during acertain period on a selected section of road and the total vehicle-kilometres overthe same period and section. Friction numbers for each road section weremeasured by the Dutch standard test method (86% slip). Wet friction numberswere used for all accidents that occurred in wet weather, and dry friction numbersfor those accidents that occurred in dry conditions. Figure 4.5 shows therelationship between friction level and accident rate.30 VTI meddelande 911A
Figure 4.5 Accident rate (mean and standard deviation) against friction level.In the Federal Republic of Germany [49] a regression analysis between frictionnumbers and accidents was based on the proportion of accidents that occurredunder wet conditions. In general, on most road sections the proportion ofaccidents in the wet, i.e.P w = (A w /A t ) × 100 (%)A w : Number of accidents in wet conditionsA t : Total number of accidents (in wet and dry conditions)varies between zero per cent and approximately 50 per cent and averages about 33per cent for the road network with slightly different figures from year to year. Ifon any particular section of road the proportion of wet-road accidents significantlyexceeds this range of percentages, then this can be taken as an indication ofreduced traffic safety under wet conditions. The skid numbers (locked wheelbraking force coefficients) were measured at a speed of 80 km/h. Although thereVTI meddelande 911A 31
Page 1 and 2: VTI meddelande 911A • 2001Frictio
Page 3 and 4: Publisher:Publication:VTI meddeland
Page 5 and 6: ContentsAcknowledgementsSummary 51
Page 7 and 8: 1 IntroductionRoad friction, its me
Page 9 and 10: 3 Road friction measurementFriction
Page 11 and 12: 0,70,60,50,40,30,20,10Dense asphalt
Page 13 and 14: 3.1.1 Friction measurement devicesW
Page 15 and 16: BV11 is a trailer with the water ta
Page 17 and 18: Figure 3.7 The VTI Saab Friction Te
Page 19 and 20: Some devices use a fixed slip, like
Page 21 and 22: In Sweden mainly three friction mea
Page 23 and 24: 10 cmFigure 3.12VTI Portable Fricti
Page 25 and 26: The concept of international fricti
Page 27 and 28: Öberg [60] has compiled measuremen
Page 29: homogeneity of the surface conditio
Page 33 and 34: Figure 4.7 Histograms of locked whe
Page 35 and 36: RoadwayappearanceDriverbehaviourAcc
Page 37 and 38: A number of surveys of friction num
Page 39 and 40: Figure 4.14 Multiplier for locked-w
Page 41 and 42: Table 4.2 Accident rates at differe
Page 43 and 44: 5 References1. Instructions for usi
Page 45 and 46: slitlagerbeläggning - inverkan på
Page 47: 50. Sävenhed H: Relation Between W

Friction measurement methods and the correlation between road - VTI

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