The steering assembly is applicable to a human-driven vehicle having a chassis (1) mounted on self-orienting wheels (2). The steering assembly comprises a steering unit (50b) with a steering wheel (4) installed on a mobile support and maintained out of contact with the ground by elastic means at an end (1b) of the chassis (1), and a control unit (50a) with a command member (7) in another end of the chassis. The units are connected by transmission devices (19, 20, 21). The command member (7) is manually operable to lower the steering wheel (4) against the force of said elastic means and to make the steering wheel (4) rotate with respect to a substantially vertical shaft when the wheel (5) is in contact with the ground to steer the vehicle. The elastic means automatically lift the steering wheel (4) when the manual operation of the command member (7) ceases.