▁of ▁darkness ▁or ▁restricted ▁visibility ▁conditions . ▁These ▁fi xt ures ▁may ▁be ▁elev ated ▁or ▁in - p av ement ▁and ▁emit ▁blue ▁light ▁normally . ▁Where ▁a ▁four - way ▁intersection ▁cross es , ▁the ▁light ▁at ▁the ▁centre ▁of ▁the ▁crossing ▁may ▁be ▁om n id irection al ▁and ▁emit ▁yellow ▁light . ▁Where ▁a ▁road ▁for ▁ground ▁vehicles ▁only ▁meets ▁a ▁tax i way ▁or ▁at ▁an ▁end ▁of ▁us able ▁service ▁area ▁for ▁a ▁r amp ▁or ▁tax i way , ▁the ▁light ▁at ▁the ▁edge ▁of ▁the ▁road ▁or ▁the ▁final ▁tax i way ▁edge ▁light ▁may ▁emit ▁red ▁light . ▁▁ ▁Tax i way ▁Center line ▁L ights : ▁They ▁are ▁steady ▁burning ▁and ▁emit ▁green ▁light ▁located ▁along ▁the ▁tax i way ▁center line . ▁Where ▁a ▁tax i way ▁cross es ▁a ▁run way , ▁or ▁where ▁a ▁" le ad - off " ▁tax i way ▁centre line ▁leads ▁off ▁of ▁a ▁run way ▁to ▁join ▁a ▁tax i way , ▁these ▁lights ▁will ▁alternate ▁yellow ▁and ▁green . ▁ ▁Clear ance ▁Bar ▁L ights : ▁Three ▁in - p av ement ▁steady - burn ing ▁yellow ▁lights ▁installed ▁at ▁holding ▁positions ▁on ▁tax i ways ▁Run way ▁Guard ▁L ights : ▁Either ▁a ▁pair ▁of ▁elev ated ▁flash ing ▁yellow ▁lights ▁installed ▁on ▁either ▁side ▁of ▁the ▁tax i way , ▁or ▁a ▁row ▁of ▁in - p av ement ▁yellow ▁lights ▁installed ▁across ▁the ▁entire ▁tax i way , ▁at ▁the