Traffic was MUCH BETTER in the 1970s. Only a few spots in Marin on 101 were slow. Sonoma 101 at the time had some slow spots at peak hours (not periods) between Petaluma and Novato. NWP hauled plenty of gravel and lumber, with a little local business (part of PS&R still ran, occasionally). I was there in the mid-70s, then again in the mid-late 80s. By the late 80s, the SRosa-SF commute was getting pretty bad (with a couple of disconnected HOV lane segments in Marin), but it still moved; yes, still better than it is now at least in central/northern Marin and in Sonoma Co. Mid-80s is when GGT should have instituted a reversible bus lane through San Rafael on the by then abandoned NWP r/w, connecting the HOV segments, but the politics and money and vision weren't there.

The last time I was through there near (early part of) the peak period (last fall), traffic was pretty good once on the bridge up to about Corte Madera. Stopped there and trickled very slowly (even in the HOV lane) through San Rafael up to Novato. That was different from what I remembered - used to be more SF-oriented traffic in southern Marin. So I'd expect that for Marin-Sonoma regional traffic, SMART is a no-brainer (it's not on the freeway) if commute trips can even remotely work using it. It'll fill up. The need for another connection to SF, though, is more questionable.