Apparently it does happen every now and then with this type of design. One of the major bridges going into Boston is cable-stayed and there have been (a very few) news reports over the years about falling ice. But it doesn't seem to be regarded as a major ongoing problem (and any bridge is going to have opportunities for ice to fall on vehicles under the right (wrong) circumstances).

I'd imagine the size of the bridge itself might be a factor. The two in question in Vancouver (Alex Fraser/Port Mann) would dwarf the Zakim bridge (that's what I'm assuming you are talking about).

I suppose an engineer would have more input on this though, I really don't know too much about bridge design.

The Port Mann Bridge has it's pillars in the middle between the traffic lanes, and the cables splayed outward across the lanes of traffic. The bridge pictured in this article has it's pillars outside the span, with cables running parallel to traffic instead of above it. Should mitigate a lot of the problems Vancouver has.

Alex Fraser has cables on the outside, and the same issues, if not worse.

https://goo.gl/images/XogwUa

The (mighty) Mackinac Bridge in Michigan has had similar problems recently. It's a suspension, not a cable-stayed bridge, fwiw.

http://www.mlive.com/news/index.ssf/2017/04/mackinac_bridge_...

So... The straights of Mackinac but the Mackinac bridge.

Pronounciation help needed.

It is true of all modern design. The smoother the lines, the fewer the parts, the larger the blocks and more direct the fall. Make the bridge look like a spiderweb and all that will fall is now. Make it a monolith and you get 100kg blocks.

Could you have little automatically-run cable wipers that slid down periodically and were retracted.

Here is a link that you may find interesting http://www.iaarc.org/publications/fulltext/P2-7.pdf

That's exactly what they do in Vancouver, actually. To various degrees of effectiveness.