The Sydney Harbour Bridge goes approx north-south and, when opened in 1932 had, from west to east, two railway tracks, six lanes of road traffic and two tramway tracks.
When Sydney did away with trams in the 1960's the two tram lines were replaced with road traffic making 8 lanes for cars all on the one level. (John, it is not a two level bridge.)
Interestingly, Sydney had its first test run of a new light rail route this week from the City to Kensington in the eastern suburbs. It already has another tramway (again called the light rail) which goes from the City to the inner western suburbs. I think there are some assets on the DLS which show the light rail rolling stock and the route.
The Sydney Suburban Rail service has 8 car electric trains which service the northern suburbs via the bridge. The line drops very quickly on the south side to go underground below York Street in the central city. The older suburban trains with only one drive axle per bogey (the famous Red Rattlers) used to struggle up this slope in the afternoon peak period when full of commuters. I remember many occasions when the wheels were slipping on this hill. On a couple of occasions the train came to a standstill, and struggled away again VERY slowly. I worked in the city and commuted to/from Pymble on the North Shore for many years.