The Operational Street Pollution Model (OSPM®) is a widely used air quality model for urban street canyons. It is a parametric model, simulating the contribution from traffic emissions on a single street at receptor points at the buildings' facades. The OSPM contains a number of empirical parameters, accounting for processes such as emission factors or dispersion of pollutants. The values of these parameters are based on empirical assumptions, and might not be optimal for a specific street. In this work, we allow these parameters to vary within a certain meaningful range.