The paper presents a quantitative analysis of the impact of travel speed on the number of accidents and level of pedestrian safety. With the use of the calculation capabilities of the so-called “Power model”, it was demonstrated that it is reasonable to introduce limited zones of max. 30 km/h in cities. The quantitative comparison of the level of risk of death and injury of pedestrians and cyclists at AIS3+ for mean speeds obtained in Poland in 2014 by vehicles in built-up areas and on expressways and motorways was presented by using the statistical relation demonstrating the dependency of risk from speed. The procedure of determining the impact of vehicle speed estimation error on the error of the determined risk was presented taking into consideration the fact that vehicle speed is one of the mostsignificant parameters.