A roadside crash cushion, comprising: a guide rail fixed to a road surface; a plurality of sliding supports which slidably engage along the guide rail; a plurality of collapsible tubular elements, which are made of a metal and/or a composite and/or a plastic material, which are arranged horizontally one following another, which are supported by the plurality of sliding supports and which each have a straight development axis and are fixed to the plurality of sliding supports; wherein each collapsible tubular element of the plurality of collapsible tubular elements has a length and a transversal section that are in a relation to one another such as to determine an irreversible compressive deformation of the collapsible tubular element which determines the collapse thereof along the development axis thereof when the collapsible tubular element is subjected to an axial force that is at least equal to a critical force value; wherein each sliding support of the plurality of sliding supports comprises a fixing plate and a carriage which is connected to the fixing plate and which engages with the guide rail; the roadside crash cushion being characterized in that: it comprises a plurality of connecting plates that are used in substitution in a certain corresponding number of sliding supports of the plurality of sliding supports and that only have to separate two consecutive collapsible tubular elements for ensuring that they axially incur the plastic compressive deformation; each collapsible tubular element of the plurality of collapsible tubular elements is provided with: a first end fixed to the fixing plate of a first sliding support of the plurality of sliding supports or to a first connecting plate of the plurality of connecting plates; a second end fixed to the fixing plate of a second sliding support of the plurality of sliding supports or a second connecting plate of the plurality of connecting plates. a guide rail fixed to a road surface; a plurality of sliding supports which slidably engage along the guide rail; a plurality of collapsible tubular elements, which are made of a metal and/or a composite and/or a plastic material, which are arranged horizontally one following another, which are supported by the plurality of sliding supports and which each have a straight development axis and are fixed to the plurality of sliding supports; wherein each collapsible tubular element of the plurality of collapsible tubular elements has a length and a transversal section that are in a relation to one another such as to determine an irreversible compressive deformation of the collapsible tubular element which determines the collapse thereof along the development axis thereof when the collapsible tubular element is subjected to an axial force that is at least equal to a critical force value; wherein each sliding support of the plurality of sliding supports comprises a fixing plate and a carriage which is connected to the fixing plate and which engages with the guide rail; the roadside crash cushion being characterized in that: it comprises a plurality of connecting plates that are used in substitution in a certain corresponding number of sliding supports of the plurality of sliding supports and that only have to separate two consecutive collapsible tubular elements for ensuring that they axially incur the plastic compressive deformation; each collapsible tubular element of the plurality of collapsible tubular elements is provided with: a first end fixed to the fixing plate of a first sliding support of the plurality of sliding supports or to a first connecting plate of the plurality of connecting plates; a second end fixed to the fixing plate of a second sliding support of the plurality of sliding supports or a second connecting plate of the plurality of connecting plates. it comprises a plurality of connecting plates that are used in substitution in a certain corresponding number of sliding supports of the plurality of sliding supports and that only have to separate two consecutive collapsible tubular elements for ensuring that they axially incur the plastic compressive deformation; each collapsible tubular element of the plurality of collapsible tubular elements is provided with: a first end fixed to the fixing plate of a first sliding support of the plurality of sliding supports or to a first connecting plate of the plurality of connecting plates; a second end fixed to the fixing plate of a second sliding support of the plurality of sliding supports or a second connecting plate of the plurality of connecting plates.