A method to assess the safety of a driving style of a terrestrial vehicle , the method comprising the steps of: - detecting , during a first operating phase of the vehicle , at least a quantity associated with an operating condition of a device of the vehicle ; - establishing a function that associates said quantity with a score expressing a degree of safety of the operating condition; and - determining , during said first operating phase, the score on the basis of at least the detected quantity, through said function; the safety of the driving style being assessed , during said first operating phase, on the basis of the determined score, wherein: - said step of detecting comprises detecting a plurality of quantities respectively associated with operating conditions of corresponding devices of the vehicle; - said step of establishing comprises establishing a plurality of functions that respectively associate said quantities with respective scores expressing corresponding degrees of safety of the associated operating conditions; and - said step of determining comprises determining the scores on the basis of the respective detected quantities, through the corresponding said functions; wherein the safety of the driving style is assessed, during said first operating phase, on the basis of each of the determined scores and/or on the basis of an overall score determined as a function of the determined scores, the method being characterised in that said quantities are defined by a first portion and a second portion of said quantities; the method furthermore comprising the steps of: - determining the existence of a second operating phase of the vehicle , different from said first operating phase, and in which detecting said second portion produces unreliable information; - detecting , during said second operating phase, said first portion of said quantities; - determining , during said second operating phase, a portion of said scores on the basis of the respective quantities of said first portion through the corresponding functions; the safety of the driving style being assessed , during the second operating phase, on the basis of each of the determined scores and/or on the basis of a further overall score determined as a function of the determined scores. - detecting , during a first operating phase of the vehicle , at least a quantity associated with an operating condition of a device of the vehicle ; - establishing a function that associates said quantity with a score expressing a degree of safety of the operating condition; and - determining , during said first operating phase, the score on the basis of at least the detected quantity, through said function; - said step of detecting comprises detecting a plurality of quantities respectively associated with operating conditions of corresponding devices of the vehicle; - said step of establishing comprises establishing a plurality of functions that respectively associate said quantities with respective scores expressing corresponding degrees of safety of the associated operating conditions; and - said step of determining comprises determining the scores on the basis of the respective detected quantities, through the corresponding said functions; - determining the existence of a second operating phase of the vehicle , different from said first operating phase, and in which detecting said second portion produces unreliable information; - detecting , during said second operating phase, said first portion of said quantities; - determining , during said second operating phase, a portion of said scores on the basis of the respective quantities of said first portion through the corresponding functions; <EOS>