A commenter on this post on Westside traffic asked if peak hour data might show different patterns, so I created similar graphics for the same roadways using the same data (Caltrans publishes peak hour, peak month, and yearly average traffic).
I’ll let the graphics speak for themselves. The peak hour patterns are quite similar to the total volume patterns, including the structural changes on the 405 and Venice coinciding with completion of the freeway widening project between the 90 and the 10. It’s actually a little surprising to see so much of a change in peak hour volumes – I would have guessed that changes in total volumes would be reflected in a shorter peak, leaving the peak hour itself relatively unchanged, rather than a more uniform change. These facilities are all near capacity, so if more cars enter the systems, peak volumes can only go up so much, and the increase would be expressed as a longer peak period and greater total delay.
I’ve put the daily volumes & peak volumes side by side so you can easily compare. Note that the y-scales are necessarily quite different. As always, click to embiggen.