Road test correlation with

Correlation with Road Test Ratings of Compounds.718... 

Correlation with Truck Tire Road Test Ratings.753... 

The following laboratory surfaces have given high correlations with a wide range of road test data ... 

However, a correlation with road test ratings can often be improved if an independent term of log V is added to the transformation variable log a-jv. The friction or side force coefficient can then be written as... 

Figure 26.42 compares the correlation coefficient between a road test on wet concrete and the laboratory side force measurements of the six compounds of Table 26.2 on blunt, wet Alumina 180 (a) with a log oxv-log v evaluation and (b) with a temperature-log v evaluation. It appears that the... 

FIGURE 26.42 Comparison of the correlation coefficients between laboratory side force measurements with the six compounds of Table 26.2 on wet, blunt Alumina 180 and a concrete road test track as function of log ajv and log v (left) with function of temperature and log v (right). 

It is seen that a good agreement is only reached if equal shp conditions are assumed, with a correlation coefficient of 0.977, demonstrating also how misleading tire road test results can be if multi-section tires are used or tires of different stiffness due to either different constmctions or modulus differences of the tread compounds. 

The question of the influence of the road surface on tire wear cannot be answered unequivocally because of the large number of different compositions, state of use, and weather influences on their abrasive power. Road surfaces are also not durable enough for laboratory use. Hence, reliance has to be placed on the correlation between laboratory results on a laboratory abrasive surface and road test experience. Alumina of different grain size (but primarily 60) has proved to be the most useful. Even its sharpness changes with time of use and disks are limited in their useful life. 

Results from continuing in-service evaluation of all test roads are being collected and used to develop comprehensive design and application recommendations as well as correlations with analytical and theoretical laboratory analyses. 

Wear is important in applications as diverse as tires, conveyor belting, footwear, and windscreen wiper blades, yet most of us would accept that the rubber industry still awaits a laboratory test or series of tests that can predict service performance with any confidence. Over the years, there certainly has been no shortage of small-scale tests for abrasion resistance and indeed no shortage of claims or reports of satisfactory correlation with the behavior of various products, but strong doubts remain, and some sectors, not least the tire industry, conclude that there is no substitute for a service trial or a simulated product test, for example, a road trial on tires held at a small slip angle to accelerate wear. 

Automotive companies have used a four-poster road simulator rig with environmental conditioning to establish correlations with conventional adhesive testing methods [71]. 

As mentioned earlier, Hakkinen (1958) employed various psychological tests for discriminating levels of accident proneness. He succeeded in establishing a very stable accident criterion due to the homogeneity in road hazards. The accident records of these subjects provided a retest reliability with split half correlations of the first four years/second four years and odd/even years (in brackets) bus drivers r = 0.58 (0.68) tram drivers r = 0.67 (0.73). 

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