Dynamic speed-controlled automatic turn signal cancellation in a vehicle. An automatic turn signal cancellation system is configured detect steering wheel angle changes to indicate a vehicle turn and then a steering wheel angle returning towards turn neutral position for canceling turn signal. If steering wheel angle remains in the turn neutral position for a determined stability time, the turn is deemed completed and the turn signal is automatically cancelled. The stability time is dynamically determined inversely related to maximum steering wheel angle of the turn, because a steering wheel will return to a stable position faster from a larger steering wheel motion from a sharper turn. The automatic turn signal cancellation system can also dynamically set a threshold angle used to determine initial vehicle turn based on the speed of the vehicle because the faster the vehicle speed, the less steering wheel angle change is required to perform a turn.

An autonomous travel controller detects whether a host vehicle is carrying out a first course change for changing a course in a direction indicated by a turn indicator. Upon detecting that the host vehicle is carrying out the first course change, detecting whether there is a road that enables a second course change for changing the course of the host vehicle that branches from the road after the first course change. When a road that enables the second course change is detected, the autonomous travel controller turns the turn indicator off.

An autonomous travel controller detects whether a host vehicle is carrying out a first course change for changing a course in a direction indicated by a turn indicator. Upon detecting that the host vehicle is carrying out the first course change, detecting whether there is a road that enables a second course change for changing the course of the host vehicle that branches from the road after the first course change. When a road that enables the second course change is detected, the autonomous travel controller turns the turn indicator off.

A turn signal switch device that can immediately execute a function different from blinking of a turn signal, and prevent an erroneous operation. The turn signal switch device includes an operation knob configured to be swing-operable along an extending direction of a handlebar, and operable in a direction vertical to the swing direction and extending toward an upper side of a vehicle, in which, if the operation knob is operated in the rising direction, the turn signal executes a lighting mode different from blinking of the turn signal that is performed by the swing operation, and after the operation knob is operated in the swing direction, tor the rising direction, the operation knob returns to a neutral position at which the operation knob is held at a non-operated timing of the operation knob.