6 ▁km / h ; ▁ 2 3 - 3 5 ▁m ph ). ▁ ▁High - speed ▁exit ▁ ▁Bus y ▁air ports ▁typically ▁construct ▁high - speed ▁or ▁rapid - exit ▁tax i ways ▁to ▁allow ▁aircraft ▁to ▁leave ▁the ▁run way ▁at ▁higher ▁spe eds . ▁This ▁allows ▁the ▁aircraft ▁to ▁vac ate ▁the ▁run way ▁quick er , ▁perm itting ▁another ▁to ▁land ▁or ▁take ▁off ▁in ▁a ▁shorter ▁interval ▁of ▁time . ▁This ▁is ▁usually ▁accomplished ▁by ▁making ▁the ▁exit ing ▁tax i way ▁longer , ▁thus ▁giving ▁the ▁aircraft ▁more ▁space ▁in ▁which ▁to ▁slow ▁down , ▁before ▁the ▁tax i ways ' ▁up coming ▁intersection ▁with ▁another ▁( per pend icular ) ▁tax i way , ▁another ▁run way , ▁or ▁the ▁r amp / t arm ac . ▁ ▁Mark ings ▁ ▁Normal ▁Center line ▁A ▁single ▁continuous ▁yellow ▁line , ▁ ▁to ▁ ▁in ▁width . ▁ ▁En hanced ▁Center line ▁The ▁en hanced ▁tax i way ▁center ▁line ▁mark ing ▁consists ▁of ▁a ▁parallel ▁line ▁of ▁yellow ▁dash es ▁on ▁either ▁side ▁of ▁the ▁tax i way ▁center line . ▁Tax i way ▁center lines ▁are ▁en hanced ▁for ▁ 1 5 0 ▁feet ▁( 4 6 ▁m ) ▁before ▁a ▁run way ▁holding ▁position ▁mark ing . ▁The ▁en hanced ▁tax i way ▁center line ▁is ▁standard ▁at ▁all ▁F AR ▁Part ▁ 1 3 9 ▁cert ified ▁air ports ▁in ▁the ▁USA . ▁Tax i way ▁Edge ▁Mark ings ▁U sed