Post #396: Courthouse traffic trend?

At last night’s Transportation Safety Commission (TSC) meeting, there was a lot of complaint about rising levels of traffic on Courthouse.  And I have to say, that matches my perception.  I see afternoon rush hour backups at the Maple/Nutley light that reach past Meadow Lane playground.  And … I just don’t recall seeing that a few years ago.

Long story short, VDOT data show no upward trend in traffic on Courthouse Road.  This probably comes as a surprise to the people who live on Courthouse.  It certainly goes against my perception of traffic on Courthouse.  But the numbers are what they are.

VDOT traffic counts are available on this page.  Please note that while they show a count for every year, for every monitored street, it looks like they only do an actual measurement (for Courthouse) every third year.  In-between, it looks like they just just gap-fill by trending the data forward.

Here’s the VDOT count of average weekday traffic, every third year from 2003 to 2018, in cars per day:

So I just thought I’d throw that out there.  I have a few ideas of what might be causing this, but it’s hard even to guess as to how to support or refute any proposed explanation.

Just to forestall one possible argument, the peak hour traffic is no more concentrated now than it was back in 2003.  Throughout this period, just under 10% of the daily traffic occurred during the peak hour of the day.

So what’s the explanation? One way to explain it is that everybody is wrong.  Traffic hasn’t picked up.  Traffic was actually worse in 2003, on Courthouse, than it is today.  Perception and memory can be flawed, so you can’t rule that out.

Otherwise, I’m stumped.  I just can’t quite picture a plausible scenario where an increasing number of cars is getting onto that street, but evading the VDOT traffic counter.

Perhaps traffic is more concentrated for very brief periods of time, leading to brief (but extreme) backups.  Those “micro-bursts” of traffic would then make an impression that we would tend to remember.

Could the recent (2016?) re-timing of the Maple Avenue lights have anything to do with this?  Could that have bunched traffic up more effectively on Courthouse?

 Here’s my best guess.  I noted earlier that we really have a large number of tear-downs going on in the Town of Vienna (Post #308).  Could the deep PM backups at the Courthouse/Nutley light be a “quitting time” phenomenon?  In effect, we now have a large local workforce of construction workers.  My vague recollection (from one summer working as a carpenter’s helper) was that, come 5 PM, that’s quitting time.  And everybody knocks off.  So I wonder if we have enough of a local construction labor force now that it is affecting the “peakiness” of traffic on Courthouse.  Not enough to materially raise the daily counts, say.  But just enough, added at around the same time, into the existing PM rush hour, that it materially boosts the length of the backup at the Nutley/Maple light.  And I then  perceive those long (but short-lived) lines of cars as “traffic sure has gotten a lot worse”.

No way to validate that one way or the other.  But for sure, the hard numbers in this case are strongly at odds with the common perception.