The other two traffic lanes on the Sydney Harbour Bridge are used for the Cahill Expressway , which run only southbound on the bridge .
The Bradfield Highway currently carries six lanes of traffic across the eight lane Sydney Harbour Bridge .
The other two traffic lanes on the lane     are used for the Cahill Expressway , which run only southbound on the bridge .
The Bradfield Highway currently carries six lanes of traffic across the eight lane Sydney Harbour Bridge .