Generally, two-pass lining systems are used for transportation tunnels constructed using the New Austrian Tunneling Method (NATM). The initial lining can support a significant portion of the long-term ground loads and thus reduce the design loads on the permanent lining. This load-sharing phenomenon has traditionally been neglected, but considering load sharing in design can result in significant cost savings. This paper discusses the basic principles of load sharing in two-pass lining systems and proposes a rational method for design. Practical application of the load sharing design approach in a NATM tunnel project, the Caldecott Fourth Bore, is presented.