Palo Alto has quite a few as well. Some are just marked with signs, many have physical barriers allowing only bikes and large trash collection vehicles to easily pass.
There are barriers that restrict traffic based on dimensions - such as the 'bus trap' [1] that only allows wide vehicles, and the 'sump buster' [2] that only allows high-ground-clearance vehicles through.
Of course, these have the disadvantage that (a) they damage the cars of confused motorists [6] (b) cars stuck in traps obstruct busses anyway[5], and (c) large SUVs and pick-up trucks can drive over them anyway [4].
Another option is a powered rising bollard [3] or barrier together with some mechanism (tag, ANPR, keypad) for recognising authorised vehicles. Which avoids a lot of those weaknesses - at the cost of power and maintenance.
A fair stretch of Bryant St. is bike-limited, with narrow barriers every few blocks.
I used it in my bike commute from Sunnyvale to Menlo (which also used pedestrian/bike bridges that cross the creeks that define the Mtn View / Palo Alto and Palo / Menlo borders).
