Category: Professional

If you had asked me yesterday, “Bill, can you prevent pedestrians from crossing a bridge during construction?” my answer would have been “Sure.” And I would have been wrong wrong wrong:

From the 2009 Manual on Uniform Traffic Control Devices (MUTCD):

04. If the TTC [Temporary Traffic Control] zone affects the movement of pedestrians, adequate pedestrian access and walkways shall be provided. If the TTC zone affects an accessible and detectable pedestrian facility, the accessibility and detectability shall be maintained along the alternate pedestrian route. [emphasis added]

Aha! This has implications because on one of my projects. I am proposing to close a bridge across an interstate for a weekend. During this time, I have to figure out how to get people over, under, around, or through the construction.

One idea is to set up a van shuttle from one side to the other, using the detour route. We shall see.

I had not been aware of that particular mandate in this most recent version of the MUTCD. Just goes to show that even “experts” don’t always know everything.

Cross posted from Talking Traffic. Go there to comment.

Alluding to yesterday’s post concerning the inaccuracies in an Atlanta Journal Constitution article about Ramp Meters, I have an anecdote:

My wife and I go to plays at Oglethorpe University in Atlanta every few months. In order to get there from our house (during rush hour), we avoid the interstates and use surface streets (Johnson Ferry Road, for those of you in the area). We’ve made this trip often enough at the same approximate time that we know what the traffic is like and yesterday we encountered an unusual hang-up as we approached Interstate 285.

The traffic engineer in my cannot let things like traffic backups slide. I began speculating out loud as to the cause of the congestion: wrecks, congestion on the interstate, signal being out, whatever. After 10 minutes or so, we arrive at the interchange and I see it: The Ramp Meters are On!

I laughed. This was the first day that this particular ramp meters was activated and I had totally forgotten.

I predict that there will be a lot of complaints forwarded to the DOT concerning the congestion (on the approach streets) caused by the meters. This sort of project always needs tweaking when it’s first implemented. I opine that the observed congestion (by yours truly) was a bit excessive, but it was only day one. We’ll see how it all falls out. Hopefully, the AJC won’t run with the complaints and publish anything scathing. Give the DOT a chance to get the kinks worked out. This will improve traffic flow in the area.

Comments at Talking Traffic

In case you’re new to me or this blog, I am a traffic engineer. Better yet, I’m a certified traffic engineer: a Pee-Toe (PTOE, Professional Traffic Operations Engineer). This involves doing several different things like studying how new construction will effect affect existing traffic patterns. Typically, we look at the current year, whatever year the construction will occur, than then some arbitrary horizon year, like 20 years out.

One of our tools is called Corsim CORSIM, and leaving out all the niggly details, we get pretty simulations like this:

Argh. What a mess. Methinks I need to work on how the signals are timed at the intersections you see.

1311 Update: What a terrible job I did writing this. Look at all those grammar errors…