But, though it was obviously part of a bikeway, and one that seemed to be going in my direction (I was pedaling to Fullerton for a meeting), there was nary a sign to indicate what it was, where it went, or how to get onto it.
This is all too typical of Los Angeles and its environs. In the same city--Whittier--I passed several signs pointing right or left from Whittier Bouelvard itself, where I was riding, and indicating "Bike Route." But no indication of where said bike route might lead--just the sign and a lonely arrow.
Well, I keep grousing about wayfinding both publicly and behind the scenes at various government agencies concerned with such things; maybe they'll figure it out one of these days. (There's supposedly a wayfinding project underway in LA County, but no one I've asked yet seems to have details.)
Meanwhile, if you're in or near Whittier, you might check out the Whittier Greenway--I had to go online to discover its name. Looks like a pretty useful local route, and that bridge does get you over a complex and poorly-signed intersection with grace and ease. Here's the trail's webpage.