through ▁movement ▁between ▁the ▁east ▁and ▁west ▁sides ▁of ▁the ▁South ▁Ring ▁Road ▁was ▁the ▁highest ▁recorded ▁traffic ▁movement ▁at ▁the ▁round about ▁and ▁represented ▁approximately ▁ 4 0 % ▁of ▁the ▁total ▁traffic ▁using ▁the ▁round about . ▁As ▁such , ▁there ▁was ▁an ▁ur gent ▁need ▁for ▁grade ▁separation . ▁▁ ▁In ▁the ▁determ ination ▁of ▁a ▁preferred ▁scheme ▁solution ▁a ▁number ▁of ▁options ▁were ▁developed ▁and ▁evaluated ▁in ▁terms ▁of ▁environmental ▁impact , ▁safety , ▁construct ibility , ▁cost , ▁a est het ics , ▁dis ruption ▁to ▁traffic ▁during ▁construction ▁and ▁land ▁take . ▁These ▁options ▁included : ▁ ▁A ▁fly over ▁carrying ▁the ▁N 4 0 ▁South ▁Ring ▁Road ▁over ▁the ▁existing ▁round about ▁An ▁under pass ▁carrying ▁the ▁N 4 0 ▁South ▁Ring ▁Road ▁under ▁the ▁existing ▁round about ▁A ▁fly over ▁carrying ▁the ▁N 2 7 ▁Airport ▁Road / S outh ▁Link ▁Road ▁over ▁the ▁round about ▁An ▁under pass ▁carrying ▁the ▁N 2 7 ▁Airport ▁Road / S outh ▁Link ▁Road ▁under ▁the ▁round about ▁ ▁Having ▁compared ▁and ▁evaluated ▁the ▁four ▁options ▁it ▁was ▁considered ▁that ▁a ▁fly over ▁carrying ▁the ▁N 4 0 ▁South ▁Ring ▁Road ▁over ▁the ▁existing ▁round about ▁was ▁the ▁most ▁suitable ▁solution . ▁ ▁Const ruction ▁on ▁the ▁fly over ▁started ▁in ▁mid - 2 0 0 5 ▁and ▁finished ▁in ▁late ▁ 2 0 0 6 . ▁Effect ive ▁traffic ▁management ▁throughout ▁the ▁duration ▁of ▁the ▁project ▁was ▁vital ▁as ▁the ▁same ▁volume ▁of ▁vehicles ▁used ▁the ▁round