Also, (and i'm not sure if this is common in the US), here in montreal we have these electronic signs posted on the highways that tell you the traffic patterns up ahead. So you can turn off it if seems like there is a major accident.
In Southern California, the majority of the freeways were constructed over "virgin land" - many, like the 60, 91, and 57 do not parallel any existing roads at all. The old-time highways like Route 66 have become clogged city streets. For much of the freeway system, there is no available alternative to just being patient. And, a tie up on one freeway rapidly translates to a tie up on others. There are only four eastward exits from the LA basin - Routes, 210, 10, 60, and 91 - all of these have North/South Freeways that connect them (5, 110, 710, 605, 57); as soon as the word gets out that one of the Eastward freeways has a problem, traffic rapidly migrates to other three, causing them to jam up.
Briefly put - the highway infrastructure in the LA Basin is incapable of sustaining smooth flowing traffic 24/7 - during peak hours (and that's 8 hours a day) any "glitch" is instantly translated into a snarl that can be reflected throughout most of the system and can takes hours to unwind.
der Brucer