▁both ▁existing ▁and ▁alternative ▁gau ges . ▁Wood en ▁sleep ers ▁are ▁suitable ▁for ▁conversion ▁because ▁they ▁can ▁be ▁d ril led ▁for ▁the ▁re position ed ▁rail ▁sp ikes . ▁Being ▁difficult ▁to ▁dr ill , ▁concrete ▁sleep ers ▁are ▁less ▁suitable ▁for ▁conversion . ▁Con crete ▁sleep ers ▁may ▁be ▁cast ▁with ▁alternative ▁gauge ▁f itt ings ▁in ▁place . ▁Ste el ▁sleep ers ▁may ▁have ▁alternative ▁gauge ▁f itt ings ▁cast ▁at ▁production , ▁may ▁be ▁d ril led ▁for ▁new ▁f itt ings ▁or ▁may ▁be ▁w eld ed ▁with ▁new ▁f itt ings . ▁▁ ▁For ▁example , ▁during ▁the ▁conversion ▁of ▁the ▁Melbourne – Ad ela ide ▁railway ▁in ▁Australia ▁from ▁ ▁to ▁ ▁a ▁sle eper ▁with ▁variable ▁gau ges ▁and ▁a ▁revers ible ▁chair ▁for ▁the ▁P and rol ▁clip ▁was ▁used . ▁ ▁Struct ures ▁Con version ▁from ▁a ▁narrow ▁to ▁a ▁wider ▁gauge ▁may ▁require ▁en larg ement ▁of ▁ ▁the ▁structure ▁gauge ▁of ▁the ▁brid ges , ▁over pass es ▁and ▁t unn els , ▁emb ank ments ▁and ▁cut s . ▁The ▁minimum ▁curve ▁radius ▁may ▁have ▁a ▁larger ▁radius ▁on ▁bro ader ▁gau ges ▁requiring ▁route ▁devi ations ▁to ▁allow ▁the ▁minimum ▁curve ▁radius ▁to ▁be ▁increased . ▁Track ▁cent ers ▁at ▁stations ▁with ▁multiple ▁tracks ▁may ▁also ▁have ▁to ▁be ▁increased . ▁Con version ▁from ▁narrow ▁to ▁standard ▁gauge ▁means ▁several ▁changes ▁not ▁because ▁of ▁the ▁gauge ▁itself , ▁but ▁in ▁order ▁to ▁be ▁compatible ▁with ▁the ▁structure ▁gauge