sunnyfreckles.. the 405 freeway goes from northern los angeles where it splits from the 5 freeway (that goes from mexico to canada), and makes its way down through los angeles following the contour of the state-ocean border all the way down to south-Irvine, in Orange County.
it's generally a 5lane +carpool lane traffic on both sides.. though it can get smaller, or larger depending on the city/county it's in.
the traffic (and jokes) is horrendous. Where the 405 and 10 freeways intersect is one of SoCal's "Crush" zones.. called Crush for it's incredibly dense traffic in that one area, and it disappears (slightly) before and after. On any given day, on any given hour, at any given point of the 405, you are guaranteed to run into some sort of traffic. and for us, "light traffic" means there are about 1-200 cars per mile stretch.
Heavy traffic during peak hours (6-8am and 4-7pm) could run about 4-500 cars per mile stretch.
btw, these numbers are totally guesstimated. i'm on the 405 a lot for work/home commute, but even then, i'm only on it for like 5 miles. those 5 miles usually take me about 30 minutes to go to work, and an hour to get home. crazy right?
the 405 was built to relieve congestion from the 5 freeway. the 5 is FAR worse. the 5 at best has 5 lanes including carpool, and at worst has 2 lanes with no carpool.