The period marks the consolidation of queueing theory around diffusion-approximation methods for heavy traffic and universal performance relationships, notably linking average queue length, arrival rate, and sojourn time in a single, broadly applicable framework. Researchers favored analytically tractable models that could be extended to networks of queues and closed systems, enabling practical performance estimates across manufacturing, telecommunications, and service industries. The methodological shift toward stochastic-process-based analysis fostered cross-domain applicability and set the stage for later networked-queueing theory.