At least in Southern California, population continues to grow, and generally demand for trips grows with population, so congestion is going to tend to increase

At least in Southern California, population continues to grow, and generally demand for trips grows with population, so congestion is going to tend to increase over time. There's other factors in demand for trips, like congestion went way down during the peak of covid, and typically drops during a recession, and return to the office increases congestion, etc. But mostly it's more people; hold population steady and congestion will be more stable.