"The AASHTO load-equivalency factors strictly apply only to axles supported at each end by dual tires. Recent increase in steering-axle loadings and more extens

"The AASHTO load-equivalency factors strictly apply only to axles supported at each end by dual tires. Recent increase in steering-axle loadings and more extensive use of single tires on load-bearing axles have precipitated efforts to examine the effect on pavement wear of substituting single for dual tires." https://www.fhwa.dot.gov/reports/tswstudy/TSWwp3.pdf https://www.fhwa.dot.gov/reports/tswstudy/TSWwp3.pdf