Note 1: The busy hour is determined by fitting a horizontal line segment equivalent to one hour under the traffic load curve about the peak load point.
Note 2: If the service time interval is less than 60 minutes, the busy hour is the 60-minute interval that contains the service timer interval.
Note 3: In cases where more than one busy hour occurs in a 24-hour period, i.e., when saturation occurs, the busy hour or hours most applicable to the particular situation are used. Synonym peak busy hour.
Source: from Federal Standard 1037C and from MIL-STD-188