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Polyester (PET) strap MSE walls are gaining popularity in many countries. The writers compared measured tensile reinforcement loads from instrumented field walls under operational (working stress) conditions with predictions using the Coherent Gravity Method and the Simplified Stiffness Method. These methods are specified in the latest AASHTO code in the USA for MSE walls constructed with inextensible (steel) and extensible geosynthetic reinforcement materials, respectively. Review of the literature shows designers have used the Coherent Gravity Method for PET strap MSE walls in some cases. The paper demonstrates that the Simplified Stiffness Method is accurate for PET strap walls while the Coherent Gravity Method is excessively conservative. The paper reviews the accuracy of candidate pullout models for PET straps. A non-linear pullout model proposed by the writers in an earlier publication is shown to be more accurate than linear and bi-linear models in the AASHTO code specified for other reinforcement materials.