These specifications are intended for the design, evaluation, and rehabilitation of highway tunnels and for the design of tunnels constructed using cut-and-cover, bored, mined, and immersed tunnel construction methodologies. Provisions are not included for water conveyance, utility, transit, or rail tunnels, or shafts. Structures internal to tunnels that support roadways over ventilation plenums, roadways, or other openings in the tunnel are to be designed in accordance with the AASHTO LRFD Bridge Design Specifications (see related item), including the loadings specified here that are unique to tunnels. The load effects of these internal structures shall be applied to the tunnel lining, walls, or other supporting members in accordance with these specifications. Retaining walls for retained cut approaches to tunnels should also be designed in accordance with the AASHTO LRFD Bridge Design Specifications.