A reversing assistance device for a vehicle, the vehicle comprising a radar unit mounted on a rear of the vehicle and configured to provide distance information (R, α) to an object that is fully or partially behind the vehicle when approaching the object under an approaching angle α, characterized by: an evaluation unit configured to provide a reversing support function by: - obtaining from the radar unit the distance information (R, α) to the object, wherein the radar unit is configured to measure a closest distance R and an approaching angle α from the radar unit to a reflection point of a first return signal; - determining, based on the distance information (R, α), a shortest longitudinal distance C between a corner of the rear of the vehicle and the object along a reversing direction y of the vehicle; and the evaluation unit is further configured to determine: - a longitudinal distance F between the rear of the vehicle and the reflection point on the object measured along reversing direction y, by using: F = R × sin α, wherein R is the closest distance R and α the approaching angle; - the lateral distance b between the radar unit and the reflection point measured along a lateral direction x by using: b = R × cos α, wherein R is the closest distance and α is the approaching angle; - the shortest longitudinal distance C, by using: C = F + (b-a) × b/F, wherein "a" is a distance from the radar unit to a rear corner of the vehicle, wherein the closest distance R from the radar unit to the object represents the propagation path of the first return signal, and the line of the closest distance R has a rectangular angle with a surface plane of the object. the vehicle comprising a radar unit mounted on a rear of the vehicle and configured to provide distance information (R, α) to an object that is fully or partially behind the vehicle when approaching the object under an approaching angle α, characterized by: an evaluation unit configured to provide a reversing support function by: - obtaining from the radar unit the distance information (R, α) to the object, wherein the radar unit is configured to measure a closest distance R and an approaching angle α from the radar unit to a reflection point of a first return signal; - determining, based on the distance information (R, α), a shortest longitudinal distance C between a corner of the rear of the vehicle and the object along a reversing direction y of the vehicle; and the evaluation unit is further configured to determine: - a longitudinal distance F between the rear of the vehicle and the reflection point on the object measured along reversing direction y, by using: F = R × sin α, wherein R is the closest distance R and α the approaching angle; - the lateral distance b between the radar unit and the reflection point measured along a lateral direction x by using: b = R × cos α, wherein R is the closest distance and α is the approaching angle; - the shortest longitudinal distance C, by using: C = F + (b-a) × b/F, wherein "a" is a distance from the radar unit to a rear corner of the vehicle, wherein the closest distance R from the radar unit to the object represents the propagation path of the first return signal, and the line of the closest distance R has a rectangular angle with a surface plane of the object. - obtaining from the radar unit the distance information (R, α) to the object, wherein the radar unit is configured to measure a closest distance R and an approaching angle α from the radar unit to a reflection point of a first return signal; - determining, based on the distance information (R, α), a shortest longitudinal distance C between a corner of the rear of the vehicle and the object along a reversing direction y of the vehicle; and - a longitudinal distance F between the rear of the vehicle and the reflection point on the object measured along reversing direction y, by using: F = R × sin α, wherein R is the closest distance R and α the approaching angle; - the lateral distance b between the radar unit and the reflection point measured along a lateral direction x by using: b = R × cos α, wherein R is the closest distance and α is the approaching angle; - the shortest longitudinal distance C, by using: C = F + (b-a) × b/F, wherein "a" is a distance from the radar unit to a rear corner of the vehicle, wherein the closest distance R from the radar unit to the object represents the propagation path of the first return signal, and the line of the closest distance R has a rectangular angle with a surface plane of the object.