LOS is expressed as letter grades A through F. Per the HCM, LOS is defined as “a quantitative stratification of a performance measure or measures representing quality of service.” Service or performance measures are specific MOEs selected for the project which will be classified into LOS grades. Typically, LOS grades of A-D represent acceptable MOE values, LOS E represents near the failure range of the MOE, and LOS F represents conditions which are failing or past the failing threshold of the specific MOE.