Re the Costa Mesa Freeway: I just know that Caltrans is going to do something stupid. Adding a fourth lane to the existing roadbed is a very reasonable and relatively inexpensive way of at least partially relieving the constant congestion of that road. With the addition of a fourth lane, the number of cars in each lane could be reduced by 25%.
What concerns me, however, is the possibility of using this lane only for multi-occupancy vehicles such as buses or car pools. In driving back and forth to work each day on this road, I haven't seen a bus in at least two months. It also doesn't take much of a survey to notice that at least 95% of the cars during the most congested times have only a single occupant.
I therefore can envision at the conclusion of construction long lines of traffic in the existing three lanes with only an occasional vehicle in the new fourth lane. This will only add to the frustration of being in stop-and-go traffic and be a great temptation to break the law and cross over the line.
The diamond lane experiment on the Santa Monica Freeway in Los Angeles proved to be a fiasco and I would hope that Caltrans would have learned by that experience.