Slow, when we get a major ice storm here on the northeast coast the biggest threat is downed power lines due to the tree branches being overwhelmed with ice and coming down on the wires. The tree branches are suspended in the cold air and tend to collect the ice, whereas the ground is generally warmer so the ice buildup is less of an issue.
Most municipalities have the equipment and budget to handle spreading salt and sand that makes the roads passable in short order.
As you move down the coast it is relative. The communities that see frequent storms are better prepared than the ones that only see occasional storms, so it depends on the severity and location of the storm.
Where I live we have a naval submarine base with lots of navy housing and ship's crews moving into and out of the region. After the first severe storm of the season it is pretty easy to spot the crunched up cars of the people who are not familiar with driving in winter conditions. They come from areas that do not have severe winter weather.
When I was a kid and first got my license at 16, one of the things we would do is to go out early after a storm and do donuts in parking lots and drive on snowy roads before the plows had everything cleared. It was a lot of fun and helped us to learn where the limits of traction were. We were driving junk beaters, too, so it did not matter so much if we crunched a corner or two.
Today, with all of the 4-wheel/all wheel drive vehicles, and modern traction control, I am still amazed at the people who go flying by not aware that every car has 4 wheel brakes... and it still does not stop when it is icy.
The east coast is not in isolation. When my sister and I were in Benton City WA a few years ago we encountered a winter storm and the logical thing to do was slow down. When we got passed on the highway by someone driving at full speed like everything was normal, I said to my sister, "that guy is going to end up in the ditch", and sure enough, about a half mile down the road we watched him spin out into the median gully, taking another car with him when he went, and it was just a light dusting in a very dry region.
Slow down. Make smooth even corrections. Apply the brakes early and gently so as not to lock any wheel. Keep moving if you can, momentum is your enemy and your friend.
