This paper presents a method to determine if a usable wheelchair accessible route in a facility exists using motion-planning techniques. We use a ‘performance-based’ approach to predict the performance of a facility design against requirements of a building code. This approach has advantages over the traditional ‘prescriptive’ code-based approach for assessing acceptability of designs, which is normal practice today for assessing wheelchair accessibility. The prescriptive method can be ambiguous, contradictory, complex, and unduly restrictive in practice, and it can be ad hoc and difficult to implement as a computer application. The performance-based approach directly models the actual possible behaviors of an artifact (in this case, wheelchair motion) that are related to the functional intent of the designed system (a building) and (hopefully) to the specification of a prescriptive building code. This paper presents example cases from architectural practice to illustrate the use of robot motion-planning techniques for wheelchair accessibility analysis. This application is an example of using modern computational methods in support of knowledge-intensive engineering. The simulation method has broad applicability within engineering design. We illustrate and discuss how to analyze virtual simulations of the detailed behavior of a designed artifact in order to assess its use by intended users.