1. Device for warning drivers of automobiles of excessive speed of turning around a curve, so that they may be alerted in taking remedial measures, comprising sensing means including an arrangement of mercury switches, each one of said switches comprising a cylindrical tube within which is freely reciprocatingly moving a mercury bulb and alarm audio and/or visual signal producing means activated by said switches, the device being characterized by that: it is an autonomous, self-powered, compact device with said sensing means and said audio and/or visual signal producing means being located within one single main housing portion ( 1 ) including a rear cavity ( 12 a ) for the installation of battery means ( 12 ) for providing an independent energy supply for operation of the device and including closure means of a frontal panel surface ( 1 a ) extending into a perpendicularly projecting basement ( 1 b ); said sensing means comprising two, alternatively activated and differentially calibrated, pairs of mercury switches, each said pair comprising two oppositely inclined mercury switches for monitoring right and left turns of the vehicle, wherein a first pair of said pairs of mercury switches ( 18, 19 ) is adapted for use in conditions of dry road surface by calibration of said mercury switches ( 18, 19 ) at a predetermined value of inclination and a second pair of said pairs of mercury switches ( 20, 21 ) is adapted for use in conditions of wet road surface by calibration of said mercury switches ( 20, 21 ) at a different predetermined value of inclination, each one of said mercury switches being fixedly mounted within a lateral cavity of cylindrical carrier means ( 18 a, 19 a, 20 a, 21 a ) respectively, said cylindrical carrier means ( 18 a, 19 a, 20 a, 21 a ) respectively extending into rotatable knobs ( 18 b, 19 b, 20 b, 21 b ), said rotatable knobs being used in the calibration procedure of said mercury switches, and said device being accompanied with a calibration device for selectively adjusting response sensitivity of each one of said mercury switches ( 18, 19, 20, 21 ) into corresponding combination of performance characteristics of different vehicles and particular driving habits and skills of individual drivers.