A steering system for an autonomous vehicle, said steering system comprising: a steering mechanism having a steering mechanism input member and a steering mechanism output member, said steering mechanism being configured to translate rotation of said steering mechanism input member into movement of said steering mechanism output member which is configured to affect the position of a steer tire of said autonomous vehicle, thereby affecting the lateral position of said autonomous vehicle; a steering wheel which provides a mechanical input to said steering mechanism input member from an operator of said autonomous vehicle; a steering actuator which rotates to apply torque to said steering mechanism, thereby inducing movement of said steering mechanism output member which affects the position of said steer tire of said autonomous vehicle; and a variable coupling member operatively between said steering actuator and said steering mechanism which is configured to vary the torque that can be transmitted from said steering actuator to said steering mechanism, characterized by a means for selectively coupling and decoupling said steering wheel from said steering mechanism input member by at least: coupling said steering wheel to said steering mechanism input member when in a manual mode of operation or in a first autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is low; and decoupling said steering wheel from said steering mechanism input member when in a second autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is high, and an input device determining if an operator is contacting the steering wheel, wherein said means is engaged in dependence of an output of the input device. a steering mechanism having a steering mechanism input member and a steering mechanism output member, said steering mechanism being configured to translate rotation of said steering mechanism input member into movement of said steering mechanism output member which is configured to affect the position of a steer tire of said autonomous vehicle, thereby affecting the lateral position of said autonomous vehicle; a steering wheel which provides a mechanical input to said steering mechanism input member from an operator of said autonomous vehicle; a steering actuator which rotates to apply torque to said steering mechanism, thereby inducing movement of said steering mechanism output member which affects the position of said steer tire of said autonomous vehicle; and a variable coupling member operatively between said steering actuator and said steering mechanism which is configured to vary the torque that can be transmitted from said steering actuator to said steering mechanism, characterized by a means for selectively coupling and decoupling said steering wheel from said steering mechanism input member by at least: coupling said steering wheel to said steering mechanism input member when in a manual mode of operation or in a first autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is low; and decoupling said steering wheel from said steering mechanism input member when in a second autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is high, and an input device determining if an operator is contacting the steering wheel, wherein said means is engaged in dependence of an output of the input device. coupling said steering wheel to said steering mechanism input member when in a manual mode of operation or in a first autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is low; and decoupling said steering wheel from said steering mechanism input member when in a second autonomous mode of operation in which the torque that can be transmitted from said steering actuator to said steering mechanism is high, and an input device determining if an operator is contacting the steering wheel, wherein said means is engaged in dependence of an output of the input device.