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TRB's National Cooperative Highway Research Program (NCHRP) Web-Only Document 260: Proposed Refinements to Design Procedures for Geosynthetic Reinforced Soil (GRS) Structures in AASHTO LRFD Bridge Design Specifications explores the effect of adopting a closely?spaced reinforcement layout in geosynthetic?reinforced soil structures. While research since the early 1980s has identified the beneficial effect of closely?spaced reinforcement in reinforced soil structures, such improvement in performance is not accounted for in the simplified methodologies established by the American Association of State Highway and Transportation Officials. Considering the effect of closely?spaced reinforcement may be particularly relevant in critical structures, such as load?carrying geosynthetic?reinforced MSE (GMSE) bridge abutments, which eliminate the use of deep foundations to support the bridge loads. In fact, the adoption of closely?spaced reinforcement was identified as being particularly relevant for these type of structures, leading to specific design guidelines developed by FHWA for structures that became identified as Geosynthetic?Reinforced Soil Integrated Bridge System, or GRS?IBS.