Bicycle boulevard entrance
Bicycles can enter via the cutout, but cars can only exit. It looks to be quite popular at rush hour. At Yukon & 10th Streets in front of City Hall in Vancouver, B.C. (Here's a close-up of what a "bike sleeve" like the one at right looks like, and here's a nearby, raised example perhaps better suited to snowy areas.)
A survey of regular and potential cyclists in Vancouver found that bicyclists prefer bicycle boulevards to every other kind of on-street bikeway.