▁signs ▁until ▁the ▁control ▁tower ▁gives ▁clear ance ▁to ▁proceed . ▁ ▁Run way ▁signs ▁– ▁White ▁text ▁on ▁a ▁red ▁background . ▁These ▁signs ▁identify ▁a ▁run way ▁intersection ▁ahead , ▁e . g . ▁run way ▁ 1 2 - 3 0 ▁in ▁the ▁photo ▁above . ▁Fre quency ▁change ▁signs ▁– ▁Usually ▁a ▁stop ▁sign ▁and ▁an ▁instruction ▁to ▁change ▁to ▁another ▁frequency . ▁These ▁signs ▁are ▁used ▁at ▁air ports ▁with ▁different ▁areas ▁of ▁ground ▁control . ▁Hold ing ▁position ▁signs ▁– ▁A ▁single ▁solid ▁yellow ▁bar ▁across ▁a ▁tax i way ▁indicates ▁a ▁position ▁where ▁ground ▁control ▁may ▁require ▁a ▁stop . ▁If ▁two ▁solid ▁yellow ▁bars ▁and ▁two ▁dashed ▁yellow ▁bars ▁are ▁encountered , ▁this ▁indicates ▁a ▁holding ▁position ▁for ▁a ▁run way ▁intersection ▁ahead ; ▁run way ▁holding ▁lines ▁must ▁never ▁be ▁crossed ▁without ▁permission . ▁At ▁some ▁air ports , ▁a ▁line ▁of ▁red ▁lights ▁across ▁a ▁tax i way ▁is ▁used ▁during ▁low ▁visibility ▁operations ▁to ▁indicate ▁holding ▁positions . ▁An ▁" inter rupted ▁lad der " ▁type ▁mark ing ▁with ▁an ▁" IL S " ▁sign ▁in ▁white ▁on ▁red ▁indicates ▁a ▁holding ▁position ▁before ▁an ▁I LS ▁critical ▁area . ▁ ▁L ights ▁ ▁For ▁night ▁operations , ▁tax i ways ▁at ▁many ▁air ports ▁are ▁equ ipped ▁with ▁lights , ▁although ▁some ▁small ▁air ports ▁are ▁not ▁equ ipped ▁with ▁them . ▁ ▁Tax i way ▁Edge ▁L ights : ▁used ▁to ▁outline ▁the ▁edges ▁of ▁tax i ways ▁during ▁periods