There are 38 raised plates on the new 520 Bridge bike lane apparently covering expansion joints. At least 28 of them are on the original section of the bridge – the western high-rise and approach ramp have fewer plates and most of them are wide. The original section has closely spaced narrow plates that are humped-up so that you want to get out of the saddle when you hit them at a normal speed. Instead of replacing the bumps with flat ones, or instead of mounting them flush with the trail surface, WSDOT installed a sign warning cyclists of the hazard ahead.
The I-90 bridge has fewer expansion joints and no covers on the main bridge. On the east channel bridge there are covers, but they are flat and flush with the trail surface. (They don’t have as many bolts holding them down as the new 520 ones do so they make noise but no real bump when you go over them.)
It’s possible that the design of the plates on the 520 bridge was intentional to save money or to better drain water or something, but in terms of user utility it was a really dumb design. Unless the idea was to employ “hostile architecture” to slow people down…