For individuals who have worked in both the U.S. railroad and non-rail sectors, their Social Security benefits directly reduce the Railroad Retirement Tier I benefit. This is because Tier I is designed to correspond to what Social Security would provide and already incorporates all career earnings. However, the Railroad Retirement Tier II, which is an additional pension based solely on railroad service, is never reduced by Social Security. This coordination prevents two Social Security-equivalent benefits from being paid on the same combined career record.