Momentum v strength doesn't scale linearly.
Just some bad highway design. Also places like the Embarcadero interchange at the 101 in Palo Alto has existing traffic fighting with entering traffic within 200 meters of space. HOV lanes make it even worse because you end up squeezing all the lanes and you create incentives for HOV drivers to merge all the way to the left as quickly as possible which further delays the main lanes since people are getting slowed down from the lane changes. Then, when HOV drivers have to exit, again they have to merge all the way right again. There is a bottleneck squeeze and the lateral squeeze happening as well. Houston traffic by comparison is “bad” but far better than the Silicon Valley version despite Silicon Valley having a smaller population and fewer cars.
Exit before/ merge after we much better than exit after/merge before. SV has many of these congestion building ramp strategies.