Sticking to the point of the thread, I have to imagine their is ways of making it so that traffic flows more easily in the downtown core. Yes, driver habits and more mass transit help, but I am sure there is ways of physically it easier. I'm just tossing into the wind here, but I'm thinking about it.
One idea I have in mind is making some places where roads pass above or underneath each other, like in Los Angeles, allowing traffic to move more easily on the roads. For example, Adelaide could drop down into a trench just before Church Street and stay low under Church, Yonge, Bay and York, before rising back to street level just before University Avenue. Doing this on streets with streetcar lines is more of a hassle, as it would require the streetcar lines to be elevated above the roads. FYI, the sidewalks here would be unaffected, as they aren't going below ground level, thus businesses don't have to change anything to their storefronts. Could be an issue with parking garage exits, but that can be worked out I would imagine.
In some places, scramble-type crossings might work, too, or maybe even pedestrian bridges over the busiest of roadways, allowing for less congestion caused by pedestrian crossings.
One other idea might be to find a spot on the edge of the core and build a massive parking garage, an enclosed, climate controlled one with security, allowing people to park there for a pittance, and connect it into the PATH system. Thus, those who choose to walk a few blocks save a bunch on parking (not to mention less risk of their car getting stolen than many open lots) and reduce congestion in the core.
Rossi's Tunnel idea should be studied. I'm not sure I support that idea fully, but if it can be done to reduce traffic congestion it should at least be considered. Cost and local concerns should be fully involved, too. Junk the idea of tearing down the Gardiner - yeah, it's an ugly SOB, but we can change that easily enough, and tossing that many cars onto surface streets would make a bad problem worse. An idea there might actually be expanding it, adding two lanes in each direction above the current surface (or better, underground below Lakeshore, but that would be expensive to build) for express traffic, with a express-collector shift every four exits or so. I am aware that would be a challenge to build, but I'm just kicking ideas out here.
Yeah, more Mass Transit would be good. (I've already explained my views on Transit City.) but its not gonna solve everything, and for suburban dwellers like me it doesn't do a whole lot of good. Planning a city's transport system cannot be done entirely based on transit users or car drivers. You need to think about both, think about all forms of transport in the city.