Many urban areas designate commuter lanes to partially achieve a similar goal.
A major element of QoS in data networks is a realization of the A2 scenario. If a single application exceeds the network resources available, QoS generally will be of little help. Likewise, if there is no way to differentiate multiple competing data flows, then QoS control mechanisms have no way to prioritize traffic and no way to ensure resource availability. What QoS is QoS is a way of providing differentiated service classes and priority levels for data flows. QoS can assign priority levels and then attempt to provide these differentiated services for data flows or specific hosts.