The western half of this trail is mostly dirt road, with a touch of singletrack, going over Acalanes Ridge. The eastern half is a paved trail following the Mokelumne Aqueduct (which is actually massive twin pipes that are underground along most of this trail).
This portion of the Briones to Mount Diablo Trail
provides part of the short (roughly four-mile) connection between the eastern end of the Lafayette Ridge Trail
and Pleasant Hill/Contra Costa Center BART station. This allows a one-way ride down and out on Lafayette Ridge Trail
with a bit of extra dirt thrown in. This is also part of the legendary BADD ride (Briones, Acalanes, Diablo, Diamond, as in Black).