In ITU-R M.1390,
Calculate Traffic/Useres
Units: call-seconds
This parameter is defined as the probability that the user is “offhook” and active in the busy hour for a circuit-switched call or a packet-switched session. It is clearly defined in Erlangs (call-seconds/3600) for circuit-switched services and for packet-switched services has the equivalent unit of average relative activity in a period of reference of the busy hour.
Traffic/Useres= Busy_Hour_Call_Attemptses* Call_Durationes* Activity_Factores
When Traffic/Useres is defined in Erlangs,BHCA=（Traffic/Useres）/（Call_Durationes* Activity_Factores）
Call_Durationes is the time to to read the dialed number and determine routing or call holidng time?