Traction — not too bad really. Of course you have to watch out for slick spots, but they salt the roads and cycle paths here. It destroys both cars and bikes faster, but it’s certainly effective.

(Danes complain about the salt — Neither Sweden nor Norway, both considerably colder and less flat than Denmark, salt their roads, but neither of those countries have as many bikers either.)

Also, although it’s counter-intuitive, thin tires are better on ice than fat tires (this is true for both cars and bikes). A thin tire exerts more force in a smaller area, resulting in a more stable contact patch. So I leave my mountain bike at home and take my city bike in icy or snowy weather.