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The majority of wheelchairs delivered in less-resourced settings fail prematurely. This issue has been recognized by the WHO Guidelines that recommend product testing based on field conditions to evaluate and improve wheelchair quality. This work is motivated from WHO’s recommendation and this is first scientific study investigating inclusion of environmental conditions in wheelchair testing. The goals of this work were to develop a testing protocol for wheelchair casters based on field conditions, evaluate the impact of environmental testing factors on quality and make appropriate recommendations for wheelchair testing based on study outcomes. In this study, an evidence-based approach was followed in which wheelchair testing evidence, expert advice, and field evidence were continually triangulated to inform the testing protocol development. A literature review (Chapter 1) was carried out and expert advice was sought to generate a list of testing methods with environmental factors based on outdoor failures. Caster system failure was identified as a key testing gap that poses significant safety risks to the wheelchair users. Development of a caster testing equipment (Chapter 2) and a caster failure checklist (Chapter 3) was carried out through an iterative design and review approach. The checklist was distributed for collecting failure data following psychometric evaluation and revisions. Testing factors of shock, corrosion and abrasion were validated to respective field exposures and caster testing was conducted (Chapter 4). Environmental factors impacted the durability of 25% caster models and altered failure modes for 75% models. Two-thirds of the altered failure modes have significant risk of causing injuries to users and wheelchair failures. About 73% of the testing failures matched with the most common failure modes experienced in the field. Based on study findings, environmental factors strongly influence both the time-to-failure and failure mode for caster models. We recommend that environmental exposure need to be considered as part of wheelchair testing protocols to help improve the external validity of the testing, which will ultimately improve the safety and reliability of the device. These recommendations are discussed along with caster design recommendations and suggestions for future work in Chapter 5.