Operating speed is one of the leading safety risk factors, which increases accident risk and influences accident severity. Speeding is the leading cause of accidents and the most common road traffic offense. The key measures of speed control are educational activities and engineering traffic calming measures. This paper presents an investigation of trapezoidal speed humps – one of the traffic calming measures – and their impact on the driver and the occupants of the vehicle. The level of discomfort to the driver and the occupants, caused by vibrations when the vehicle passes the speed hump, was determined during experimental research. The discomfort level, calculated by three methods, indicated the leading cause of discomfort generated by the analysed trapezoidal speed humps.