Numerical modelling of visibility through smoke, during a fire incident inside a building, is required by most standards regarding fire protection, including the NFPA in North America and EN-45545 in Europe, to determine how well emergency signs can be seen. The smoke visibility data must then be communicated effectively to allow for proper planning of smoke management and evacuation paths. Interpretation of this data is difficult because smoke visibility only indicates how much sight is impaired at local points in space and does not give a clear sense of the cumulative effect of smoke along a sightline. Therefore, how is it possible to effectively communicate how far an occupant can see through smoke by presenting smoke visibility data alone, as it is often done in practice? The solution resides in overlaying sightlines directly on the smoke visibility data. The limit of any given sightline passing through smoke can be obtained by numerical integration along the corresponding streamline of a carefully crafted vector field. The resulting method is applied to the case of a fire incident in a train station to evaluate tenability along an evacuation path. This makes the communication of the smoke visibility data more effective by decreasing the time needed for a clear, repeatable, and consistent interpretation of the results. An automated procedure can then be created to produce the desired amount of additional data with little extra effort making it an indispensable tool for multidisciplinary teams in fire engineering.