A safety assurance system is disclosed for use in road vehicles. The system comprises a generator for providing a warning signal in response to a predetermined condition such as dozing of the driver. A rest signal is generated when the road vehicle is at rest, and a reset switch enables the driver to manually provide a reset signal. A first alarm signal is provided which is generated in response to the warning signal until the rest signal is generated. Also provided is a second signal which is generated in response to the warning signal until the rest signal or reset signal is generated. Thus, warning signals are generated that are terminated automatically when the vehicle comes to a stop or are terminated by manual operation of a reset signal.