We went into Oakland at about 2 p.m. Friday, and returned through the Caldecott a little after 3 and the eastbound lanes were already backed up to the Rockridge BART station. But when we exited the tunnel, there was no backup and everyone was at or above the limit. The tunnel is definitely a choke point, and it’s mostly because it’s narrow and dark. The new #4 bore is probably almost four lanes wide (striped down to two) in and of itself, and people fly through it. Just wonder when they decide the old tunnel needs to be replaced, what they will do because it will have to be taken out of service to be rebuilt.
They could simply try to widen the bores — admittedly taking them out of service temporarily, like you said — like was done to the tunnels on I-70 near Denver, Colorado a few years ago.