Wednesday, June 24, 2009

Sacramento Freeway Traffic Trends: 2Q 2009

If you've had the feeling recently that traffic has gotten heavier in Sacramento over the last few weeks, you're not going crazy. Traffic data from the UC Berkeley Freeway Performance Measurement System for US99 and I5 have shown year-over-year increases during the last two months, with I5 clocking a 19% jump last week alone:

Traffic data for this segment of I5 only goes back to 2006. For the curious, here is the full trend for US99 going back to 2001:

(The US99 data is much noisier than the I5 data for some reason, probably having to do with capacity issues.)

While traffic is indeed increasing vs 2008 on both freeways, it is still well below peak levels in June for previous years. June 2009 US 99 traffic is 10.3% below the highest June value (reached in 2003!), and June 2009 I5 traffic is 7.3% lower than the June 2006 value.


Anonymous said...

So we're not looking at the increase in I5 traffic over last years closure due to work on the boat section (see the note on the chart regarding the 2008 reduction) ???

I think they need to look at this all together as right now the XY 50 freeway has heavy construction on it and I can see anybody who can bypass it would (from EG taking I5 to downtown and or around to 80 instead of 99 to 80).

Sometimes they just need to leave the cubicle to analyse the stats. Remember, these are the same folks who design some of our favorite merges!


Max said...

I get the raw data from PEMS, but the y-o-y comparisons and analyses were mine, so fire your slings and arrows at me. :)

What we're looking at is a relatively static variable (vehicle-miles driven) in an otherwise highly dynamic system. When alternatives exist (trip timing, rerouting, avoidance), they will used, which makes near term predictions impossible.

What I found interesting about the I5 closure last year was how little it effected traffic on 99. Most of the closures happened at night, and there were relatively few commute periods impacted, especially southbound.

Also of note, the y-o-y increases began less than a year after the closures began. Obviously we'll know more once 3Q is over, but to me this looks like a meaningful increase in traffic.

Anonymous said...

Sorry about that, first cup of Java hadn't kicked in, or maybe I was mourning Farah or something.

The original drop off could be related to dropping residential construction as labor and materials originate up and down 5 and ended up in elk grove, west sac, woodand, natomas, plumas etc....all but shut down over the winter but maybe 25-35% recovery since.

OK, back to CALTRANS. Considering they are the transportation agency for one of the largest economies in the world, I expect that they would use properly trained statisticians to analyze the data, not just some extra engineers they have on hand with access to Excel and not rely on the graphic artist to help us form an opinion. I would expect them to release the analysis with the data.

Max, over here in the blogosphere, I would hold you to a different standard, afterall, you're a volunteer.

With that said, I have more respect for your looks at the data over the past 3-4 years, and I've learned much from you, Lander, CR, the other guy who helps you, even AB ...while all the pros and ivy league grads who missed it coming while they were paid to watch.


Max said...

No worries. My post wasn't exactly well-worded. You get what you pay for, eh? :)

while all the pros and ivy league grads who missed it coming while they were paid to watch.

I think Peggy Noonan was onto something when she opined that prozac and zoloft may have lead to excessive risk taking on Wall Street. I think there's another dimension to antidepressant-caused complacency: dispassion and conflict avoidance. It's not that people are afraid to rock the boat; it's that rocking the boat doesn't even cross their minds.