Numerous reports this morning of traffic accidents due to very slippery roads out there. Especially the farther east you drive. And bridges, of course.
One technique is to drive slow and gently tap your brakes and see if you slip a little, a lot or not at all. But ice patches are often invisible so keep your speed down. By the way, 4-wheel drive doesn’t help enough to matter. Studded tires and chains are the only things that offer enough additional traction to matter.