Originally Posted by
chas58
..............I’ve never really needed them in the city, so you may be just fine in Boston. Generally there is too much traffic (and plowing and salt). Black ice forms best when the surface is undisturbed for a while. But you may just be getting lucky so far. Watch for those shadows on cold days.
Plowing and salt increase the incidence of black/slick ice, because they cause melting and refreezing. The salted section on the local bikeway is the most prone to black ice (with bridges coming in a near second); fortunately I don't ride that section.