let's take you to los angeles where the traffic day of reckoning arrives. the so-called carmageddon. a ten-mile stretch of one of the nation's busiest highways closed for 53 hours. those are a lot of hours for folks down there. it began around midnight pacific time. residents have been urged for weeks to avoid interstate 405 this weekend throughout this entire weekend. nbc's george lewis has the latest for us. >> reporter: it's one of the world's busiest freeways carrying more than half a million cars on the average summer weekend. the billion dollar widening of the freeway aims at relieving traffic jams. >> great way to move people, reduce congestion and improve the air. >> to do that, construction crews have to tear down and remodel this bridge. forcing the shut down of a ten-mile stretch of the 405 this weekend. >> northbound side of the 405 freeway is going to be heavy -- >> long time radio traffic reporter tommy jarks.