It's more like 20km of traffic lights being out. These roads are our core east-west arterial roads and the landscape dictates that there aren't many other roads for the traffic to travel on. I can't say why there aren't traffic police out there, but these are once-public roads that have been privatised. Also, these roads are highways, not traffic intersections.
Point of trivia: before the current toll road company was given its mandate, our main east-west bridge (the Westgate) held the distinction of being one of the very few toll roads in the world that stopped being tolled when planned, when the cost was paid off. A few years of free travel, then this company was given the rights to the road just beyond the bridge...
It is the only uninterrupted motorway from the east to west sides of Melbourne, but not the only core arterial. There are other roads you can use to get from one side of town to the other. A lot of traffic using the tunnels is just commuter traffic from the east anyway.
The tunnels never were public roads, they didn't exist. You can still drive on pretty much the entire length of the West Gate Freeway, right up to the tunnel portals without paying tolls. There are some short sections of motorway though that were previously un-tolled but are now tolled, though there has been some pretty extensive upgrades.
That said I'm no way in favour of City Link, but the real core 'arterial' for urban commuting is our public transport system. :-)
Point of trivia: before the current toll road company was given its mandate, our main east-west bridge (the Westgate) held the distinction of being one of the very few toll roads in the world that stopped being tolled when planned, when the cost was paid off. A few years of free travel, then this company was given the rights to the road just beyond the bridge...