Group of at least two assemblies each comprising a support, at least one rail and a plurality of devices for fixing said rail to said support, said support comprising a plurality of concrete blocks, each block being integral and comprising at least two grooves, said fixing devices each comprising at least one head arranged in a groove of one of said blocks, said assemblies each comprising a plain track section, or a turnout, the plain track sections or turnouts of the first and second assemblies having different geometries, wherein at least one block of said first assembly is identical to at least one block of said second assembly, or one of the two assemblies comprises at least two identical blocks.