This article describes the safety and effectiveness issues related to signal countdown timers (SCT). These devices are used in many countries around the world. The impact of these devices on road safety and the effectiveness of traffic lights is presented. During a literature review, more than 18 aspects of device use were recognized. The research involved measurements carried out at three intersections in Płock (Poland). The initial and final period of the green signal for vehicles was analyzed. Headways, incidences of vehicles passing through after the end of the green signal, and red-light violations were examined. Additionally, a fuel consumption analysis and a case study of a road crash in Szczecin (Poland) are presented. Problems related to signal countdown timers working during traffic light failure are described. The research shows different influences of signal countdown timers at various intersections. It was observed that SCTs increase the number of red-light violations and during the red-amber signal. On the other hand, the number of entries during the amber signal with SCTs is lower. A literature review also indicated that the use of SCT causes a reduction of start-up time (positive impact) and increases vehicle speed (negative impact). The article concludes that SCTs do not always fulfill their role in improving road safety and control efficiency. Conclusions can address various stakeholders, including drivers, road authorities, and traffic engineers.

One of the elements of implemented in Poland traffic control systems is module of priorities for public transport. Essence of working priority and the basic indicators of its effectiveness were presented. Among methods for testing the effectiveness of the priority, there has been distinguished economic and simulation approach. An example of priority research based on simulation of chosen street in Bydgoszcz was shown, using Vissim simulation environment. Developed simulation model, its connection to the control system, adopted detection system and 4 tested control strategies were also described. Then, the simulation and its results were presented. In results discussion they were compared in terms of adopted control strategies. In summary, possibility of a future study extension was also indicated.