The assumption of ''zero true slippage at zero net traction'' by Upadh
yaya has given rise to a heated argument of wide interest for ISTVS en
gineers. This article discusses this argument. Using the traction pred
iction equations presented by Upadhyaya, traction data obtained from e
xperiments with a 4WD tractor in tilled Kanto loam soil were analyzed.
It was impossible to evaluate the unique values for all the parameter
s of the traction prediction equations independently. We proposed a re
gression model by reforming Upadhyaya's equations, and the regression
model fitted well with the traction data plotted. Implications of a ze
ro condition in the traction data analysis are also discussed. Copyrig
ht (C) 1996 ISTVS.