Most of his research was in the areas of tribology and contact mechanics. He also made significant contributions to the understanding of fluid rheology under elastohydrodynamic lubrication conditions.He received the International Award from the Society of Tribologists and Lubrication Engineers in 1983. He was awarded the Tribology Gold Medal from the Institution of Mechanical Engineers in 1985. He was awarded the Mayo D. Hersey Award from the American Society of Mechanical Engineers in 1991.In 1999, Johnson won the William Prager Medal awarded by the Society of Engineering Science. He was also awarded the 2006 Timoshenko Medal.