The planning of statistical examining of population within the scope of undesirable events at road intersections with three-colour traffic lights has been discussed. In particular, the problems have been raised that are related to the analysing how the installation of countdown timers showing the time left to a change in the traffic lights signal affects the traffic flow. Attention has been focused on selected research process elements that concern the preliminary works, examination proper, and statistical inference, without describing the types and engineering designs of the displays used and without dealing with the legal aspects. Selected literature items related to the subject matter touched upon have been analysed, with pointing out the practices that either might be desirable or might arouse some reservations. In the part concerning the preliminary works, such issues as the sample selection method, sample size, and selection of the variables under analysis have been discussed. As regards the examination proper, some elements of the information acquisition process have been considered in both the subject-related and object-related aspects. When discussing the statistical inference, some limitations have been pointed out that affect the conclusions drawn from the examination of statistically non-representative samples and some acceptable methods of the analysis of empirical data have been mentioned. The article has been concluded with a brief recapitulation.