Traffic signs as part of traffic control plan inform traffic participants about road conditions, dangers, limitations and other information needed for their safety on the road. The meaning of traffic signs is defined by their shape, colour and symbol. The quality of the symbol design, manifested in its simplicity and clarity, can influence the understanding of the traffic signs thus affecting the perception. The aim of the study is to investigate, using eye tracking system, the understanding of warning and mandatory signs based on relevant and measurable eye movements: total visit duration, visit count, average fixation duration and fixation count. It was found that the participants, in order to understand signs, tend to detain longer, more often look back and have more fixations on signs whose meaning is not understood. The results also show that more experienced drivers usually base their understanding on experience thus understanding faster and with less number of fixations as opposed to younger drivers.