I’m not sure that there is a direct relationship between BHCA and values that are derived using the tables. BHCA is a number that is measured and represents the number of call attempts during the busiest hour. However, in order to get an idea of the traffic, you also need to know mean holding time and ASR (Answer Seize Ratio), since for a given BHCA, the actual traffic intensity (in Erlangs or minutes or CCS or whatever) will be directly proportional to the ASR and the mean holding time. You can use all three of these figures to size a service, but these are usually measured numbers or educated guesses based on experience. Whenever I go see carriers that want to implement a service or expand an existing service, they will usually have values for BHCA, ASR, and mean holding time for which we have to design. Usually, these are numbers that they have measured. When using the Erlangs tables, you are sizing a service based on probability theory, not measured values.