Talking Traffic

Fail Blog is a compilation of user-submitted images and videos with the colloquial title of “Fail”. If you don’t know what that means, I suggest perusing the latest postings and it will become obvious.

Signage is often a topic. This one just came up and I find it horribly amusing. Unfortunately, this sort of thing is all too common.

Warning: A great deal of the subject matter on Fail Blog is not safe for work. This particular link is fine, however

Topics: National Traffic Signal Report Card, 2007 Fataliity Rates, ITE Annual Meeting

 Episode 24 - National Traffic Signal Report Card [15:25m]: Play Now | Play in Popup | Download

Topics: Autonomous Vehicles

 Episode 23 - Autonomous Vehicles [8:33m]: Play Now | Play in Popup | Download

One of the more frustrating parts of my day job is when a project requires the calculation of a Benefit/Cost ratio. This ratio is simple in concept: add up all the financial benefits of a project including the projected reductions in congestion, crashes, etc. and divide it by the amortized total cost of the project. This is a tool for evaluating whether a project is worth building. For example, if I’m proposing a project that is going to cost $1 million but it only provides the benefit of $1/2 million than the B/C ratio is 0.5. We’re getting only a 50% return on our investment, therefore don’t build it! Easy, right? Maybe. Let’s talk about where the numbers come from.

Calculating the project cost is the easy part (easy, even if it’s occasionally inaccurate due to unforseen circumstances and rising material prices). Calculating the projected financial benefits of a project can be straightforward, too, if it’s intended as a congestion relief project; there is plenty of documentation concerning reductions in delay time vs. financial benefit. Things are a bit murkier when trying to assemble a financial benefit to projected reductions in collisions because it’s hard to say whether a reduction (or increase) in collision rate is due to a project or not. Lastly, it’s nearly impossible to calculate the benefit (or impact) of a road project on the surrounding business and homes. There are broad overarching assumptions, but they are at best a WAG¹. This is why I cringe every time I’m requested to include a B/C ratio on a project. On non-capacity projects (projects that aren’t adding roadway lanes) it’s very difficult to achieve a B/C ratio of greater than 1.0 which is the assumed benchmark when someone asks for that number.

The reason for all this ramp-up is because of a news report yesterday morning in Atlanta. The Georgia Dept. of Transportation is shutting down all constructions projects (with a few exceptions) within 5 miles of a shopping mall or other retail center from Thursday to Sunday to allow for the Sales Tax holiday that Georgia is having this weekend.

My question, and I admittedly have NO CLUE, is whether the B/C ratio for this proposed work stoppage is greater than 1.0? Sure, there will be less congestion during the weekend, but does this really improve the bottom line for the taxpayer? The contractors are going to figure the cost of a 4 day work stoppage into the project cost, so it might end up at the end that this Tax Holiday congestion relief program will actually cost the state, therefore the taxpayers, more than the congestion would have.

Unfortunately, you’d have to make so many assumptions and WAGs that it’s probably impossible to say with any certainty one way or the other. It’s an interesting thought experiment, though.

Today is the one year anniversary of the I-35W bridge collapse in Minnesota. If you don’t know what I’m talking about, check out the wikipedia article. Most of the relevant info is there.

The Interstate bridge collapsed during evening rush hour on August 1, 2007. Thirteen people died and approximately 100 were injured. The reason for the catastrophic failure of the bridge has not been determined precisely, but early findings by the National Transportation Safety Board (NTSB) pointed at an original design flaw in the Gusset Plates (details here).

This tragedy has underscored a problem that the U.S. is facing: aging infrastructure requires maintenance or replacement. According to the American Society of Civil Engineers’ Infrastructure Report Card, the price of maintaining and upgrading the United States public infrastructure (roads, bridges, airports, utlilities, harbors, buildings and everything else) at an adequate level is approximately $1.7 trillion over five years (that’s $340 billion annually). Without a continued investment you run into issues such as degrading roadways, leaking sewage systems, inadequate water supplies, congested airports, etc. It is a fact that this nation continues to grow and the infrastructure representing its nerves and veins must grow with it. Look at Singapore and Manila. Those two cities are so overwhelmed by traffic congestion (to take only one example from transportation) that almost all deliveries from the ports occur at night; the trucks simply cannot move during the day. I’d hate to see that happen to Baltimore, or Savannah, or Long Beach.

$340 billion is a very big number, but let’s remember that Congress fell all over itself to send $200 million to Minnesota to replace the I-35W bridge. If they can snap-count a number that big, I think it’s reasonable to find some additional funding on an annual basis to assist the states in replacing and maintaining the existing infrastructure. 27% of the nation’s bridges are currently rated as strucutrally deficient as of 2005 (which does not mean in imminent danger of collapse, so don’t worry too much) which is an improvement from several years previously, but is too high. Unfortunately, the only way to improve that number is through funding because bridges need constant maintenance and eventual replacement to keep up with the growing traffic demand.

Do I have a proposed solution? I do not. I am not a finance geek or a politician. I, along with many others in my field, see a looming problem which if unaddressed will only lead to bigger problems in the future.

So, remember the I-35W collapse. While it apparently wasn’t directly caused by insufficient funding for maintenance, it is a bellwhether for problems to come.

Topics: Ramp Meters, Podcast Schedule

 Episode 22 - Ramp Meters [6:46m]: Play Now | Play in Popup | Download

Yes, yes. I know it’s been a while, but I finally polished up Episode 22 and will be recording it this weekend. You’ll get to have it on Monday morning, as usual.

Also, stay tuned for more changes to the blog theme. This one, unfortunately, has some issues I don’t feel like dealing with. I’ve been working on my personal blog over at The Evil Eyebrow and with some modifciations, I’ll probably use that theme. Then I don’t have to worry about two different sets of headers, stylesheets, etc.

The Theme I had originally installed on Talking Traffic was dissatsifying me. So I’ve changed it. What do you think?

I plan to alter the header image to something more transportation-engineering centric, eventually, but until then it’s a nice picture.

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.

Why do I do this Talking Traffic website, with its podcast and tidbits?

Because of this:

From the Atlanta Journal Constitution:

Ramp meters are traffic lights that are intended to control the number of vehicles entering and exiting the highway. They are to reduce traffic congestion on the ramps. [emphasis mine]

Argh! This is one hundred percent wrong! Ramp meters in no way are designed to reduce congestion on the ramps, they’re designed to reduce congestion on the highway by “metering” the input of vehicles from the ramps. Instead of a flood of vehicles entering the highway all at once, a steady one…two…three…four addition of vehicles allows the highway to avoid congestive backups. Unfortunately, this causes delays on the ramps and possibly the roadways leading to the ramps.

While your wait to get on the highway will lengthen, the time you spend on the highway itself will decrease. That is why Ramp Meters are being installed in multiple locations throughout the country.

Sounds like a podcast topic to me.