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Approach fills behind bridge abutments are commonly supported by wrap-around mechanically stabilized earth (MSE) walls. In contrast to a sloped fill, the vertical MSE wall face would tend to reduce the passive resistance provided by the abutment wall. However, the reinforcing strips provide confinement to the approach fill which would increase the passive resistance. This paper describes the first large-scale tests to evaluate passive force-deflection curves for abutments with MSE side walls. A test was also performed with fill extending beyond the edge of the abutment wall for comparison. The abutment wall was simulated with a pile supported cap 5.58 ft high, 11 ft wide, and 15 ft long in the direction of loading backfilled to 5.5 ft. The backfill behind the pile cap consisted of clean sand compacted to 96% of the modified Proctor maximum density. During lateral loading, the MSE wall panels moved outward 1.4 inches when the ultimate passive force developed. However, the passive force was still 76% of the resistance provided by the cap with fill extending beyond the edges. The normalized passive force-deflection curves for the tests with and without the MSE walls were similar and reached an ultimate at deflections of 3.8% and 4.2% of the wall height for the MSE wall confined and unconfined backfills, respectively. The measured ultimate passive force is compared to the computed ultimate passive force for the Rankine, Coulomb, log spiral and California Department of Transportation (Caltrans) methods. The log spiral method underestimated the ultimate passive resistance by 36% while the Caltrans method provided an excellent estimate.