A method for detecting a derailment of a rail vehicle, the rail vehicle comprising two or more rail vehicle parts (2,3,4,5,6) and one or more joints (10,11,12,13) by means of which adjacent rail vehicle parts are rotatably connected to each other, and the method comprising: a) determining a-1) a rotation angle (α,β,γ,δ; θ), between adjacent rail vehicle parts, and/or a quantity derived from the rotation angle (α' t, β' t, γ' t, δ' t; θ' t), or a-2) a plurality of rotation angles (α, β,γ,δ; θ) or a plurality of quantities derived from the rotation angles (α' t, β' t, γ' t, δ' t; θ' t) between different adjacent rail vehicle parts, b) comparing b-1) the rotation angle (α,β,γ,δ; θ) or the derived quantity (a' t, β' t, γ' t, δ' t; θ' t) from a-1), or several angles of rotation or derived quantities from a-2) with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U) and/or b-2) of a plurality of angles of rotation (α,β,γ,δ; θ) or of the plurality of quantities derived from the angles of rotation (α' t, β' t, γ' t, δ' t; θ' t) from a-2) relative to one another, and/or b-3) of a state value (| a(to) | - | β(t 0) |), which is determined from a plurality of angles of rotation (α, β,γ,δ) or a plurality of quantities (α' t, β' t, γ' t, δ' t) derived from the angles of rotation from a-2), with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U), wherein a test criterion as to whether a derailment is present or not is defined on the basis of - the reference value/limit value, the reference value range (-U to U), and/or the limit value range in b-1) or b-3), and/or - a desired relation (a * β < 0) of a plurality of rotation angles and/or a desired relation of the plurality of quantities derived from the rotation angles ( α' t * β' t < 0) from b-2) to each other, c) determining whether the test criterion is fulfilled or not fulfilled and whether a derailment is occurring/has occurred or is not occurring/has not occurred. a) determining a-1) a rotation angle (α,β,γ,δ; θ), between adjacent rail vehicle parts, and/or a quantity derived from the rotation angle (α' t, β' t, γ' t, δ' t; θ' t), or a-2) a plurality of rotation angles (α, β,γ,δ; θ) or a plurality of quantities derived from the rotation angles (α' t, β' t, γ' t, δ' t; θ' t) between different adjacent rail vehicle parts, a-1) a rotation angle (α,β,γ,δ; θ), between adjacent rail vehicle parts, and/or a quantity derived from the rotation angle (α' t, β' t, γ' t, δ' t; θ' t), or a-2) a plurality of rotation angles (α, β,γ,δ; θ) or a plurality of quantities derived from the rotation angles (α' t, β' t, γ' t, δ' t; θ' t) between different adjacent rail vehicle parts, b) comparing b-1) the rotation angle (α,β,γ,δ; θ) or the derived quantity (a' t, β' t, γ' t, δ' t; θ' t) from a-1), or several angles of rotation or derived quantities from a-2) with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U) and/or b-2) of a plurality of angles of rotation (α,β,γ,δ; θ) or of the plurality of quantities derived from the angles of rotation (α' t, β' t, γ' t, δ' t; θ' t) from a-2) relative to one another, and/or b-3) of a state value (| a(to) | - | β(t 0) |), which is determined from a plurality of angles of rotation (α, β,γ,δ) or a plurality of quantities (α' t, β' t, γ' t, δ' t) derived from the angles of rotation from a-2), with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U), wherein a test criterion as to whether a derailment is present or not is defined on the basis of - the reference value/limit value, the reference value range (-U to U), and/or the limit value range in b-1) or b-3), and/or - a desired relation (a * β < 0) of a plurality of rotation angles and/or a desired relation of the plurality of quantities derived from the rotation angles ( α' t * β' t < 0) from b-2) to each other, b-1) the rotation angle (α,β,γ,δ; θ) or the derived quantity (a' t, β' t, γ' t, δ' t; θ' t) from a-1), or several angles of rotation or derived quantities from a-2) with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U) and/or b-2) of a plurality of angles of rotation (α,β,γ,δ; θ) or of the plurality of quantities derived from the angles of rotation (α' t, β' t, γ' t, δ' t; θ' t) from a-2) relative to one another, and/or b-3) of a state value (| a(to) | - | β(t 0) |), which is determined from a plurality of angles of rotation (α, β,γ,δ) or a plurality of quantities (α' t, β' t, γ' t, δ' t) derived from the angles of rotation from a-2), with at least one reference value or limit value, or with at least one reference value range or limit value range (-U to U), - the reference value/limit value, the reference value range (-U to U), and/or the limit value range in b-1) or b-3), and/or - a desired relation (a * β < 0) of a plurality of rotation angles and/or a desired relation of the plurality of quantities derived from the rotation angles ( α' t * β' t < 0) from b-2) to each other, c) determining whether the test criterion is fulfilled or not fulfilled and whether a derailment is occurring/has occurred or is not occurring/has not occurred.