local fspec_t = {
      	"formspec_version[3]",
          "real_coordinates[true]",
          "size[" .. fspec_size_w .. ", " .. fspec_size_h .. "]",
          "label[2,1;" .. minetest.formspec_escape("Select a vacant seat inside the vehicle below:") .. "]"
      }
local formspec = table.concat(fspec_t)

-- result:
    formspec_version[3]real_coordinates[true]size[2.4, 8.7]label[2,1;Select a vacant seat inside the vehicle below:]button[0.2, 0.3;2, 0.5;seat_1;Seat #1]