By now you have almost certainly set your clocks back an hour, as required by the end of Pacific Daylight Time for another year. (If not, check your pockets: you misplaced an hour somewhere today.) As nice as the extra hour was this morning, we give it all back (and more) by getting home in the dark for the next four months. Condolences, everyone. Normalcy returns March 11, 2012.
From the vault: In 2005, Mickey Kaus took a stab at explaining why evening traffic is so much more congealed when the darkness comes. It's at the bottom of this lengthy, pre-permalink Kausfiles entry that's chock full of L.A. Times observations.
There are two kinds of people--1) those who run on "nature's clock," by looking at the position of the sun and how light it is; and 2) those who run on the official designated human-clock time of day.
After the switch from Daylight to Standard time--during which human clocks are set back an hour--the people who run on nature's clock and leave work late leave at what used to be 7:00 and is now 6:00. The human-clock people--the 2s--leave at their normal human-clock times. Does virtually everyone leave at 6 then? No--there are some nature's clock people who used to leave at 6 but now leave at 5:00. But (and this seems the key point) since the nature's clock people tend to be laid back folks who leave work late, there are more of them moving from a 7:00 to a 6:00 commute than there are rushed, uptight nature's clock people moving from a 6:00 to a 5:00 commute. The result is a doubling up of commuter streams at 6:00--at least until the laid-back nature's clock people realize they want to stick around the office for an extra hour in the dark. Then traffic goes back to normal.
At least I think that's what happens. Correct me if I've got it wrong. ... Update: A simpler way to put it might be that the end of Daylight Savings time makes the people who go by human clocks head home just as the sun is setting, which is when the "nature's clock" people also naturally tend to head home. Traffic is lighter (i.e., better spaced out) when the human-clock people are prompted to leave work while it is still light, letting the nature's-clockers fill the roads an hour or so later when the sun actually goes down. That's what happens with Daylight Savings Time, which is why (I'm told) traffic always gets better when it takes effect again in the spring. ... P.S.: Doesn't that mean that, if we care about growing congestion, we should keep Daylight Savings Time year round? It seems cheaper than double-decking all the freeways or trying to bribe people into carpools.
LAO in 2005: Into the darkness
Clock in Bullock's Wilshire lobby, by LA Observed