Because you literally have no where to go if something happens, it's not a good idea to change lanes (or brake or accelerate or pass, for that matter) when on a bridge, even in good weather. Always leave yourself an out. On a bridge, the only out is down.
As for driving in snow and ice, well, you really can't negotiate ice. Ice just isn't navigable at all. High school physics teaches you how to drive on snow and ice. You're dealing primarily with inertia, then friction and gravity. Newton's first law of motion says that an object in motion (or at rest) will remain in constant velocity and direction unless acted upon by an external force.
Since snow, and especially ice, affords very little friction, inertia will cause you to tend to keep on going straight. If you slow down enough to allow gravity to act in giving you additional friction, then you can gain some control and overcome some or all of the inertia. Of course, if you slow down too much, then gravity becomes the major player and it will pull you down hill, be it forwards, backwards, or to the side. (I hate it when lanes on a straightaway are overly banked left and right for water runoff, cause it's a major driving problem in snow.) Wind is also an external force that can act upon inertia, being wind from nature or wind from a high speed supertrucker who thinks he's above the laws of physics.
You just have to balance your speed based on what you're going to do. No sudden movements, since inertia and a lack of friction simply won't allow it, anyway. Many people never took physics in high school, or they did and failed it. Stay far away from these people, as the biggest problem with driving on ice and snow isn't driving on ice and snow, it's having to deal with those who don't know how to drive on ice and snow.