It is an MUP, it goes by groups of homes and people walk it. In one area it actually splits into three paths, one for cyclists, one for walkers (decomposed granite) and one for horses (shredded bark). It has signs on it that tell the cyclists to watch for walkers and horse riders. At the point where the picture was taken, this Path is quite distant from the areas of walkers and horse riders and pretty much the domain of cyclists. It is grade separated in a number of areas, and has long sight lines (cyclists can and do go fast here), but in other areas it is at grade and very much shared. The whole thing is about 15 miles long and parallels a freeway. There is no other continuous road in the area that goes where either the freeway or MUP goes.. so you either drive the freeway or bike/walk the MUP. The freeway was once a very busy local farm highway that cyclists and motorists shared... until Caltrans decided to improve the freeway. By making the road into a limited access freeway, they cut off cyclists from that corridor... Caltrans built the MUP to offer cyclists means to continue to access that corridor. The MUP and freeway connect a couple of distant communities... one being a somewhat commercial area, the other basically residential.

This Path to me represents a nearly ideal bike highway... I say nearly ideal as it is not fully grade separated and at each end it is poorly terminated. Along the way this Path connects to neighborhood roads with freeway like ramps, allowing cyclists easy ingress and egress. Bike traffic peaks twice a day, just like any freeway.

You can see this path in the map on this URL... look for the words "56 bike trail."
http://maps.google.com/maps?client=f...,0.009066&z=17