The bachelor thesis is focused on the transport of hazardous substances and possible threatening of the chosen locality in a traffic accident. The goal of the thesis is to evaluate a threatening of the chosen locality by a hazardous substances leak in a traffic accident. Lučenec District has been chosen as the investigated locality, where the main arterial road KE – ZV with a high frequency of hazardous substances transport passes through. The Toluene-diisocyanate has been chosen as the hazardous substance on the basis of the research of transported substances which was performed in two phases on the main arterial road KE – ZV. The traffic accident of a vehicle, transporting this substance near to Abovce village, is another argument for this choice. On the basis of this accident, the simulation of Toluene-diisocyanate spread at defined meteorological conditions was performed in ALOHA software. According to the graphic representation of the affected area, it can be state that this area is smaller at the windless meteorological conditions; however, the most toxic area is bigger. It is obvious that the scenario with the strong wind meteorological conditions is less dangerous for the population