A washing system of a vehicle comprising: a control unit, a platform having a longitudinal translation guide, a portal mounted in a translatable manner along said guide for the passage on the vehicle, said portal comprising at least two diametrically opposite uprights (6a, 6b) that are connected by at least one cross member, at least two support means (8a, 8b) supported slidingly by said cross member along said cross member, at least two brushes (9a, 9b), each rotating around a corresponding rotation axis (10a, 10b) hinged in aerial suspension on a corresponding support means (8a, 8b), locking means (11a, 11b) of the orientation of each rotation axis (10a, 10b) of said brushes (9a, 9b), detection means of the washing pressure exerted by the brushes (9a, 9b) on the vehicle characterised in that said control unit is programmed with at least one first washing programme part that: drives the portal from a first position to a second position on the guide by making the portal pass onto the vehicle, deactivates said locking means (11a, 11b), leaving said brushes (9a, 9b) free to oscillate so as to adapt dynamically to the shape of the sides of the vehicle during said passage, commands detection of the current value of the washing pressure of the sides of the vehicle during said passage, compares said current value of the washing pressure with a threshold value during said passage, commands reciprocal movement of said support means (8a, 8b) so as to maintain during said passage the current value of the washing pressure of the sides of the vehicle the same as said threshold value. a control unit, a platform having a longitudinal translation guide, a portal mounted in a translatable manner along said guide for the passage on the vehicle, said portal comprising at least two diametrically opposite uprights (6a, 6b) that are connected by at least one cross member, at least two support means (8a, 8b) supported slidingly by said cross member along said cross member, at least two brushes (9a, 9b), each rotating around a corresponding rotation axis (10a, 10b) hinged in aerial suspension on a corresponding support means (8a, 8b), locking means (11a, 11b) of the orientation of each rotation axis (10a, 10b) of said brushes (9a, 9b), detection means of the washing pressure exerted by the brushes (9a, 9b) on the vehicle characterised in that said control unit is programmed with at least one first washing programme part that: drives the portal from a first position to a second position on the guide by making the portal pass onto the vehicle, deactivates said locking means (11a, 11b), leaving said brushes (9a, 9b) free to oscillate so as to adapt dynamically to the shape of the sides of the vehicle during said passage, commands detection of the current value of the washing pressure of the sides of the vehicle during said passage, compares said current value of the washing pressure with a threshold value during said passage, commands reciprocal movement of said support means (8a, 8b) so as to maintain during said passage the current value of the washing pressure of the sides of the vehicle the same as said threshold value. drives the portal from a first position to a second position on the guide by making the portal pass onto the vehicle, deactivates said locking means (11a, 11b), leaving said brushes (9a, 9b) free to oscillate so as to adapt dynamically to the shape of the sides of the vehicle during said passage, commands detection of the current value of the washing pressure of the sides of the vehicle during said passage, compares said current value of the washing pressure with a threshold value during said passage, commands reciprocal movement of said support means (8a, 8b) so as to maintain during said passage the current value of the washing pressure of the sides of the vehicle the same as said threshold value.