The diamond interchange in the foreground is for Holly Drive/Mt. Carmel Drive. In newer (post-1960s) freeways, where it is necessary to have an interchange with surface streets very close to a freeway-to-freeway interchange, Caltrans will often extend the access ramps for the freeway-to-freeway stack interchange over the street interchange. That is what is going on here. Another well-known example is the Story Road interchange with U.S. Highway 101 in San Jose, which sits under the ramps to and from the interchange with Interstate 280. In such freeway-to-freeway stack interchanges, the ramps for diagonal movements between freeways can easily be more than a mile long (like the one visible here).

Photographed and uploaded by user Coolcaesar