A system for protecting a user travelling on a vehicle provided with a steering member, the steering member being configured to change a direction of movement of the vehicle, the protection system comprising: - an inflatable protective structure having an inactive state wherein said protective structure is deflated, and an active state wherein said protective structure is inflated while being configured to protect at least a part of the user's body, - an actuation device connected to the protection structure, the actuation device being configured to leave the protection structure in the inactive state as long as no accident condition is detected, and switch the protective structure to the active state when an accident condition is detected, the actuation device including a detection device configured to detect at least one actuation parameter representative of the accident condition, wherein the detection device is configured to detect a loss of control of the vehicle as an actuation parameter, when the user lets go of the steering member for a determined period while the vehicle is moving, the detection device comprising an electronic contact detection device configured to deliver an actuation signal representative of an absence of contact of the two hands of the user with the steering member, and an electronic movement detection member configured to deliver a movement signal representative of a movement of the vehicle, the actuation parameter comprising the actuation and movement signals, wherein the contact detection member comprises at least one electronic sensor configured to detect the absence of contact of the two hands of the user with the steering member, and an electronic control unit connected to the electronic sensor and configured to emit the actuation signal when the absence of contact of the two hands of the user with the steering member is detected, the protection system being characterised in that it comprises at least one fixing sleeve bearing the electronic sensor, and a casing enclosing the control unit, the fixing sleeve and the casing being configured to be removably mounted on the steering member. - an inflatable protective structure having an inactive state wherein said protective structure is deflated, and an active state wherein said protective structure is inflated while being configured to protect at least a part of the user's body, - an actuation device connected to the protection structure, the actuation device being configured to leave the protection structure in the inactive state as long as no accident condition is detected, and switch the protective structure to the active state when an accident condition is detected, the actuation device including a detection device configured to detect at least one actuation parameter representative of the accident condition, wherein the detection device is configured to detect a loss of control of the vehicle as an actuation parameter, when the user lets go of the steering member for a determined period while the vehicle is moving, the detection device comprising an electronic contact detection device configured to deliver an actuation signal representative of an absence of contact of the two hands of the user with the steering member, and an electronic movement detection member configured to deliver a movement signal representative of a movement of the vehicle, the actuation parameter comprising the actuation and movement signals, wherein the contact detection member comprises at least one electronic sensor configured to detect the absence of contact of the two hands of the user with the steering member, and an electronic control unit connected to the electronic sensor and configured to emit the actuation signal when the absence of contact of the two hands of the user with the steering member is detected, the protection system being characterised in that it comprises at least one fixing sleeve bearing the electronic sensor, and a casing enclosing the control unit, the fixing sleeve and the casing being configured to be removably mounted on the steering member. wherein the detection device is configured to detect a loss of control of the vehicle as an actuation parameter, when the user lets go of the steering member for a determined period while the vehicle is moving, the detection device comprising an electronic contact detection device configured to deliver an actuation signal representative of an absence of contact of the two hands of the user with the steering member, and an electronic movement detection member configured to deliver a movement signal representative of a movement of the vehicle, the actuation parameter comprising the actuation and movement signals, wherein the contact detection member comprises at least one electronic sensor configured to detect the absence of contact of the two hands of the user with the steering member, and an electronic control unit connected to the electronic sensor and configured to emit the actuation signal when the absence of contact of the two hands of the user with the steering member is detected, the protection system being characterised in that it comprises at least one fixing sleeve bearing the electronic sensor, and a casing enclosing the control unit, the fixing sleeve and the casing being configured to be removably mounted on the steering member.