Ethernet Ring Protection (ERP)'s ability to provide sub-50 ms failover time enhances the candidacy of Carrier Ethernet over conventional SONET/SDH as the technology of choice for packet transport networks. To ensure higher service availability, the logical ERP should be carefully designed by considering concurrent dual link failures. In this paper, we categorize the network service outages subject to concurrent dual link failures. We address the problem of optimal capacity provisioning while providing higher service availability and formulate this as an joint optimization problem. We show that higher service availability can be achieved by proper RPL (Ring Protection Link) placement and ring hierarchy selection with the objective of maximizing the network flow under any dual link failure scenario. Numerical evaluations as well as comparisons are carried out which show the effectiveness (in terms allocated capacity and service outages) of the presented design approach.