Service systems are usually classified in terms of their number of channels . A single-channel queuing system, with one server, is typified by the drive-in bank with only one open teller.
If, on the other hand, the bank has several tellers on duty, with each customer waiting in one common line for the first available teller, then it is a multiple-channel queuing system.
Same case can be considered for many situations in construction industry . Resources of repetitive construction projects and truck concrete mixer delivery are two examples.
The first figure below shows the mechanism of the procurement of resources in a repetitive construction project while the second figure shows the mechanism of the delivery of concrete by truck mixers . Both mechanisms contains queuing .