The 2025 version of CSA S6, Canadian Highway Bridge Design Code, builds on durability concepts introduced in CSA S6:19. Section 2 provides a methodology to achieve a design service life of 75 years simply by following all steps of the code. The term design service life is introduced to apply a limit states philosophy to durability design while definitions of design life, service life, maintenance, and rehabilitation were adjusted to establish clear expectations of what is anticipated and acceptable within the design service life of a structure. The service life design procedure is a significant addition that guides the designer to make appropriate decisions related to the structural system, structural details, materials, and protection systems. First, the user defines the design service life, assigns macroenvironments to the structure, and classifies exposure zones for all component surfaces. Exposure zones are described qualitatively, but some quantitative limits are provided (e.g., deicing salts splash zone, limits for soil and water aggressivity). Second, the user assesses deterioration risk by examining all deterioration mechanisms applicable to each exposure zone and material. Finally, the user applies mitigation measures that are mapped to the deterioration mechanisms through the exposure classes. Material-specific mitigation measures in the material sections are linked to exposures through a series of standard “roadmap” tables. For steel buried structures, tables assign a corrosivity category for each exposure class and the mitigation measures are linked to the corrosivity category. The design engineer applies mitigative measures consisting of avoidance, deemed-to-satisfy approaches, or special analysis and testing (including probabilistic modeling) if allowed by the owner. The procedure will minimize the risk of durability failures. This paper introduces the design service life process, focusing on corrugated steel buried structures, and presents examples of applying this procedure to corrugated buried steel structures.