It is not yours truly but PB that laid out in its ground rules for identifying potential hsr alignments that no tunnel would be mined thru an active fault. Apparently the Angeles National Forest tunnels would indeed pass thru the San Gabriel fault which is deemed inactive.

I believe the widespread rollout of electric cars will spark a renewed call to build highways, for what it is worth. Also lots of experimentation world wide in "enhanced" road systems as all- electric vehicles are vastly better suited to remote control than fossil fuel vehicles. Just the fact they will not be carrying a fuel tank that could ignite makes a big difference.