A note on the pseudo-conservation law for a multi-queue with local priority

The pseudo-conservation law for a multi-queue system with non-preemptive priority (local priority) has recently been presented in Fournier and Rosberg [9]. This note points out that the result has independently been derived in Shimogawa and Takahashi [17]. The derivation of a mean waiting time approximation based on the pseudo-conservation law is also discussed.