Abstract: An automatic differential locking system for a working vehicle having steerable front and rear wheels, which includes a selector for selecting a steering mode of the vehicle, an actuator for operating a differential locking mechanism, and a gate for sending a control signal to the actuator in response to a signal received from the selector. The gate is adapted to send a differential locking signal to the actuator upon receipt of a parallel steering mode signal from the selector. In response to the differential locking signal the actuator actuates the differential locking mechanism. Since differential revolutions of the wheels are limited at times of parallel steering, the vehicle is capable of accurate course revisions and alterations without slipping.

Abstract: A travelling vehicle equipped with obstacle detector sensors having, at the front of the vehicle body (1), a noncontact-type obstacle detector sensor (A) and a contact-type obstacle detector sensor (B), and a vehicle speed control device (20) adapted to automatically reduce the vehicle speed from a preset vehicle speed (v.sub.)0) to a predetermined vehicle speed (v.sub.1) when the noncontact-type obstacle detector sensor (A) detects an obstacle, adapted to automatically reset the vehicle speed to said preset speed (v.sub.0) when the sensor (A) does not detect the obstacle any more during such speed reduction, and adapted to automatically stop the travelling of the vehicle immediately when the contact-type obstacle detector sensor (B) detects the obstacle.