A method for estimating the travel time of a vehicle based on the determination of the state of the vehicle, comprising: - recognizing an event of start of travel as a result of the determination of a transition from an inactive engine state or vehicle-at-rest state to an active engine state or running vehicle state; - recognizing an event of end of travel as a result of the determination of a transition from an active engine state or running vehicle state to an inactive engine state or vehicle-at-rest state; and - calculating the duration of the travel according to the time elapsed between said recognized event of start of travel and said recognized event of end of travel, wherein a transition from an inactive engine state or a vehicle-at-rest state to an active engine state or running vehicle state is determined if the active engine state or running vehicle state is maintained unchanged for a predetermined first hysteresis time interval; and wherein a transition from an active engine state or a running vehicle state to an inactive engine state or a vehicle-at-rest state is determined if the inactive engine state or vehicle-at-rest state is maintained unchanged for a predetermined second hysteresis time interval, characterized in that an optimal hysteresis time interval is determined as the minimum of a curve of error probability that an actual single trip be divided into two or more separate trips as a consequence of the vehicle stop, and that two or more actual separate trips as a result of the vehicle stop be merged in a single trip, as a function of a predetermined first and second hysteresis time interval, whereby the optimal hysteresis time interval (T') is used for the determination of the travel time of the vehicle. - recognizing an event of start of travel as a result of the determination of a transition from an inactive engine state or vehicle-at-rest state to an active engine state or running vehicle state; - recognizing an event of end of travel as a result of the determination of a transition from an active engine state or running vehicle state to an inactive engine state or vehicle-at-rest state; and - calculating the duration of the travel according to the time elapsed between said recognized event of start of travel and said recognized event of end of travel, wherein a transition from an inactive engine state or a vehicle-at-rest state to an active engine state or running vehicle state is determined if the active engine state or running vehicle state is maintained unchanged for a predetermined first hysteresis time interval; and wherein a transition from an active engine state or a running vehicle state to an inactive engine state or a vehicle-at-rest state is determined if the inactive engine state or vehicle-at-rest state is maintained unchanged for a predetermined second hysteresis time interval, characterized in that an optimal hysteresis time interval is determined as the minimum of a curve of error probability that an actual single trip be divided into two or more separate trips as a consequence of the vehicle stop, and that two or more actual separate trips as a result of the vehicle stop be merged in a single trip, as a function of a predetermined first and second hysteresis time interval, whereby the optimal hysteresis time interval (T') is used for the determination of the travel time of the vehicle. a transition from an inactive engine state or a vehicle-at-rest state to an active engine state or running vehicle state is determined if the active engine state or running vehicle state is maintained unchanged for a predetermined first hysteresis time interval; and wherein a transition from an active engine state or a running vehicle state to an inactive engine state or a vehicle-at-rest state is determined if the inactive engine state or vehicle-at-rest state is maintained unchanged for a predetermined second hysteresis time interval, characterized in that an optimal hysteresis time interval is determined as the minimum of a curve of error probability that an actual single trip be divided into two or more separate trips as a consequence of the vehicle stop, and that two or more actual separate trips as a result of the vehicle stop be merged in a single trip, as a function of a predetermined first and second hysteresis time interval, whereby the optimal hysteresis time interval (T') is used for the determination of the travel time of the vehicle.