A friend sent me a link to a recent WRAL article posted yesterday about a fatal collision in Cary on Sunday, February 12th¹. Tragically, both passengers in a left-turning vehicle died when the driver crossed the path of another vehicle. This is terrible and my condolences go out to those affected by the incident. I also feel for safety engineers everywhere who feel the emptiness of failure at each reported fatality², especially the highway safety professionals who work in this jurisdiction. However, as an engineer and scientist it is of utmost importance to step back and remember a few things about working within the confines of the real world: with limited tax funds, systems are imperfect and not every collision is preventable.

Keeping these things in mind, how do traffic engineers decide if an intersection requires a traffic signal? We use a system of “warrants”, or reasons that warrant the installation of a control device. The Manual on Uniform Traffic Control Devices (MUTCD) lists nine signal warrants for varying reasons in Chapter 4C. A pdf of this manual can be found here. These reasons range from volume to school-zone related conditions and yes, even crash experience.⁴ Most generally, traffic signals are never installed without first qualifying for one or more warrants.

Why? In many cases a signal can make an intersection worse than it started! Traffic signals are often viewed in the public eye as a cure-all, when in fact they can have adverse affects on safety and efficiency: increased delay, increased traffic control disobedience, increased use of other routes such as neighborhoods (just to skip the light!), and others. The increased stops can also increase the number of rear-end collisions at the site as well.⁴ This has led to the installation of many lights that were never needed, at sites that may now be less safe, at the cost of a six figure installation. Thats right, your average 4-way simple traffic signal costs between $150,000-200,000. Plus continued maintenance from now until forever.

The Media

One of the biggest reasons that the public is so ill informed about the affects of traffic signals is the media, and we can see it in this article.² It’s not necessarily their fault that the public demands stories that move the heart, either in tenderness, controversy, or horror. But people get so caught up in political partisan biases, that many forget how easy it is to be biased to the heart instead of the mind, allowing an element of “controversy” to develop conspiracy, scheme, even frustration in the reader. Lets take a moment to analyze some of the diction used in this article:

“hasn’t met the criteria for a traffic light, despite pleas from drivers and neighbors that the intersection is too dangerous”

I’d be pulling my hair out if there was any left to pull. On the logic side, uninformed readers could assume two very incorrect conclusions: drivers and neighbors always know a dangerous intersection when they see one³, and that pleas from drivers and neighbors warrant a traffic signal. But theres so much on the emotional side as well. Using the word “plea” to stab the hearts of our readers, the author has clearly set the tone of the entire article to:

“People have begged on hand and knee, offering to sacrifice their first born for just one, ONE traffic signal. The site would be safer, and this wouldn’t have happened”.

No wonder people think traffic signals are a cure-all! This conjecture could be patently false. For all we know without adequate evidence, adding a traffic signal could make this site WORSE. But not now. As uninformed citizens we now know that the evil city of Cary is denying us the promise of safety and security that only a traffic signal can bring.

“she attempted to turn left from West Chatham Street onto Cary Parkway and crossed into the path of a Dodge Avenger.”

This one earns the reporter kudos. Notice how quickly and easily the blame of the incident could have been shifted: 1) “she unwittingly pulled in front of traffic”, or 2) “the Dodge Avenger smashed into the side of her vehicle”. Unfortunately for the reader, we don’t know the exact cause of the collision. We may never know for sure. It could’ve easily been texting or another form of distracted driving. The author calls this collision “correctible”, though as a reader we are left unsure as to whether or not it is she or her interviewee that thinks it’s correctible and why. But by calling this collision “correctible”, the public will be wondering why correctible collisions are happening at all. And they should! But they are missing an important piece of the puzzle: some intersections are more correctible than others and warrant more immediate attention and funding, of which there is a finite amount of both.

“In addition to traffic volume and other criteria, to warrant a light an intersection would need to have had five crashes that would have likely been corrected by a traffic light in a single year.”

But I have to draw the line here, this is a complete falsehood and is misreported. Intersections do not require crashes for a traffic signal. In fact, new roads are constantly being built in conjuction with signals before they are even opened. But the remark is so instigating and confusing, it left one commenter with a terrible impression of traffic safety methods. If anything should make an engineer feel like a failure, it is the terrible miscommunication with the public that can lead to this:

Let me see if I have this right….The criteria for installing a traffic light requires multiple occurrences of either property damage, bodily harm, or loss of life. The wisdom of our city fathers leaves much to be desired. carrydoggymom, February 13, 2012 7:55 p.m

Concerned Citizens

As much as a I try to avoid reading the comments section on a news website, it’s important from a public administration point-of-view to see how this fraction of the populace thinks. Some comments are enlightening, some are sad. This time, I was mostly surprised to see intelligent debate in the comments section. Mostly.

“I bet if it was the mayor’s family, there would be a light there tomorrow. What a load of bull!” bjandroxie88, February 13, 2012 7:42 p.m

Here is the advocation that, not only should tax dollars be spent willy-nilly by those in power when they find misfortune, but that politicians should make engineering decisions. There is a problem when the politically inclined try to mingle in the affairs of those who put safety first, a perfect reason why engineers should use MUTCD warrants instead of bending to political pressure from above.

“…If the vehicle was close enough to hit them, it was close enough to see and avoid.” pedsrndad, February 14, 2012 11:56 a.m

While my first instinct is inclined to agree, sight distance plays an important factor in intersection design, and it may need reinvestigation at this particular intersection. Though I imagine it was addressed and not seen as a big problem during the original design, factors such as reclassifying the speed-limit or increased volume year-to-year could play a part in changing the environment here.

The Intersection

I’ve driven the intersection myself, and especially during rush hour it can be difficult to turn left. The median supplies a little refuge, but not much. I glanced at the traffic volume maps, but without knowing more about peak hour data, it’s difficult to say exactly what warrants the intersection can qualify for. I’m surprised it doesn’t hit the peak-hour warrant, or even the school-crossing warrant with it’s proximity to Laurel Park Elementary. With the limited data I have on hand, I might recommend the following traffic studies to take another look at the signal warrants: sight distance study, spot speed study, and/or a volume study.⁵

If a light is installed in the near future, I hope it will be because it is warranted and that conditions have changed since the last inspection of the intersection. Not because of the ravings of uninformed watchers of the 6 o’clock news. We should all strive to be more cognizant of the impact media can have on the heart of the public, and how important good communication can be when working for the public sector. These efforts will make it easier to limit the affect of a tragic story in the news from opening our wallets too wide when there aren’t enough collisions to merit a new, expensive, and possibly ineffective traffic control device.

Wrap Up (Read: Important Conclusions)

By now you should have gathered the following:

• Traffic signals are not a cure-all; sometimes, when not really needed, they cause problems.
• We use Signal Warrants to come to justified conclusions, recommended by the MUTCD, on whether or not to add a traffic signal at an unsignalized intersection.
• MUTCD has 9 different signal warrants for varying reasons of safety.
• Intersections do not require collisions to warrant a traffic signal.
• “Pleas from drivers and neighbors” is not an MUTCD signal warrant.
• “The mayor found misfortune” is not an MUTCD signal warrant.
• Crashes and fatalities do not necessarily merit an MUTCD signal warrant.

References and Notes:

1. Cary intersection doesn’t meet criteria for traffic light, WRAL, Monday, February 13th, 2012
2. Mental Note: Prevented collisions never make the news. How could they?
3. Mental Note: Drivers and neighbors are an invaluable resource when discussing what they think of an intersection. However, everyone’s seen a collision somewhere. This does not always, a “dangerous” location, make.
4. Manual on Uniform Traffic Control Devices 2009, published by the Federal Highway Administration.
5. As found in the Highway Safety Engineering Studies Procedural Guide, published by USDOT and FHWA 1991, commonly referred to as “The Parker Manual”.

I had a few spare weeks recently, and decided to go on a cross-country trek to visit some friends. I also took the opportunity to take in some civil engineering landmarks along the way. First stop was Minneapolis/St. Paul, Minnesota. Had a great time visiting my college buddy Garrett, now a grad student at U of M. We passed by the Civil Engineering building on campus, a building residing almost completely underground. For it’s unique design it was awarded with the Outstanding Civil Engineering Achievement Award by ASCE in 1983.

I visited the new 1-35W Mississippi River Bridge, the replacement bridge on the site of the disastrous 2007 bridge collapse. Improper design as well as large loads from construction equipment and extra layers of pavement caused the original bridge to collapse. Nearby, I walked across the Stone Arch Bridge of Minneapolis, overlooking the only waterfall on the Mississippi river. Built in 1883 and named a Historic Civil Engineering Landmark, the bridge served as a railway bridge but now serves as a pedestrian and bicycle path across the Mississippi. In the area are many parks that serve the historic district and showcase the history of the water-powered mills that put the Twin Cities on the map.

It’s always exciting to see public transportation improvement projects, and it was neat to see the construction of new light rail stations by the local Metro Transit in St. Paul. We also visited the Town Hall Brewery and attended the Beer Dabbler Winter Carnival 2012.

Colorado

Next stop was Colorado. Not too many civil engineering landmarks on this leg of the trip. Instead, I had the wonderful opportunity to have some family in the area expose me to some really neat experiences. I went ice-fishing, fed buffalo, visited Odell Brewing, and sat in on a volunteer-firefighting training seminar. For those most interested in the sciences, here’s a nerdy exposition: you can calculate the thickness of clear ice h (inches) that can withstand failure from a load of p (tons) with the following formula: h = 4√p

There’s all sorts of other factors you can throw in for safety, and if you plan on driving out on the ice, you should probably give these a good read:

• Safety on floating ice sheets
• Ice thickness for varying load conditions

Some more neat information:

• Reports on Ice Properties and Strength
• USCAE Ice Engineering Group

Los Angeles, CA

My last stop was LA, visiting another NC State friend and former roommate, Joe. Much warmer than the previous stops, I enjoyed the beautiful sunny weather of Pasadena. I visited Venice Beach, the infamous Hollywood sign, Griffith Park Observatory, El Pueblo, Hollywood Boulevard, La Brea Tarpits, IO West Improv Club, In-N-Out Burger, and Point Fermin Lighthouse.

Of course, my visit to the locale wouldn’t do my “engineering” trek justice if I didn’t review local transportation resources. I rode both the Metro Bus and the Metro Rail, visited Union Station, and found it all to be exceptional for my use as a tourist. Joe commutes to and from work daily via Metro Rail and bicycle (which he can bring on the train) and finds them more than adequate. I was impressed with the timeliness, cleanliness, and usefulness. I only wish we had this kind of rail in Raleigh.

I also noticed the use of ramp meters both here and in Twin Cities. These are not a congestion tool we currently use in North Carolina, so I sent a quick email to Dr. Hummer, professor at NC State, with some questions on use cases and statistics. He responded rather quickly and gave me great information on the topic. They can keep the mainline traffic moving better than Level of Service “F”, preventing a 100-300 vehicles per hour per lane drop in capacity. They break up “platoons” of cars, and can decrease travel time up to 10%. In North Carolina, it’s been easier to add conventional capacity in the past, but NCDOT may need to look at ramp meters more closely for use on I-77 in Charlotte and areas around RTP.

All in all, the trip was very rewarding, and I can’t wait for the next opportunity to do a similar trip in the future. Special thanks to family and friends for taking time to spend with me and making my trip possible!

Bonus Footage

But like all things, if you do it, do it right. Cook like you mean it. Go big or go home. And recently I’ve learned that the culinary arts, or at least the kitchen responsibilities involved therein, have a lot in common with the engineering industry. It was this wonderful article on a chef’s blog that really punched it home to me: sous chefs are engineers, but not all engineers are sous chefs.

Being a sous chef has little to do with the title and all to do with what you make of it…

Cook your ass off. Organize your station better than I would. Stop whining. Turn problems into solutions. Take challenges and ride them one handed. The bull threw you? Get up and get back on. Ask for help when you need it. Rally support that’s available to you. Work cleaner every day. Create systems and implement them. Learn stations you’ve never known.

Get out of your comfort zone.

Manager or not, if an engineering office was a kitchen, everyone should strive to be a sous chef.

Think about it as you set your goals for the new year. Be the sous chef. Leave egos at home, get your hands dirty, and get cooking.

Happy Holidays everyone!

Block quote comes from the following article. Make sure you give it a read: Shuna Fish Lydon, Eggbeater Blog

“Most of the Macs today,” writes Johnson, “are being freewheeled into the office by executives, top sales reps, and other workaholics. Forrester believes this is the same demographic that we’re now calling the “power laptop user,” and according to the latest Workforce Technology And Engagement Survey, power laptop users make 44% more money, use more collaboration apps, and carry an average of three devices wherever they go.”

So much so, that these power users are willing to purchase their own Macs because the Window’s PCs supplied by their firm are slowing them down.

I know what they mean. And while I have both, I too prefer my Mac.

Via: CNN.

Happy Labor Day everyone.

While damages under 6.0 earthquakes are rare, they do indeed occur, especially in a region less known and under-designed for quakes. In fact, the area falls in a zone of very small seismic risk (see the 2012 International Building Code Map, courtesy of USGS), which is a big part of the problem. Another part of the problem is the age of these structures. Newer buildings and building methods are much safer than they used to be in this regard, but many older buildings will suffer problems, especially since there is little desire to improve them and little funding to do so.

Cause

Figure 1: Building Motion During an Earthquake (1). Click to Enlarge

What causes these damages? The lateral forces caused by the accelerating displacement of the ground. When an earthquake occurs, the acceleration of the ground will cause the building to move sideways at the base of the building. It is, after all, firmly attached to the ground in most cases, causing a lateral load and an equivalent shear force at the base (see Figure 1). The building will then begin to swing to and fro, according to the change in direction of the ground.

Familiar with Newton’s law of force? You could very simplistically apply it here to calculate the forces on the building: F = M(A), or force equals the mass multiplied by the acceleration. What may not be immediately obvious is that the higher the mass of the building, the higher the force on the building. But we CAN control the acceleration, which gives us an advantage if we play our cards right. The acceleration can be affected by the natural period of the building, or a complete oscillation, which is dependent on the building stiffness.

Supposing we could create a building that was perfectly stiff, it would match the acceleration of the ground perfectly and it would not oscillate and not experience force. This, unfortunately, is an impossibility for any material, and the slightest deformation would cause large forces due to short natural periods. So contrary to instinct, we do not want to make the stiffest buildings possible, what we want are flexible, long natural periods in our buildings. We need them to sway.

Solutions

Steel buildings have certainly come a long way, but a large part of the problem with older buildings is their dependence on stone, under-reinforced concrete, unreinforced masonry, and designs incapable of holding even the most moderate earthquake and wind loads. Many of these buildings were built at the turn of the 20th century and are still being used today.

Stone and concrete hold well under compression, but not under tension. Without an element of tension, these older stone buildings simply crumble. Newer concrete structures today are reinforced with steel, doing wonders for flexibility. When allowed to, the steel in reinforced concrete catches tension loads and transfers them. Steel is ductile, and the greater the ductility of a building, the better forces can be absorbed. When designed correctly, even after structural failure, warning signs in reinforced concrete structures are easily apparent, often allowing people to clear from the site before catastrophic failure. After all, people are more important than the buildings.

Figure 2: Deformation Components of a Reinforced Concrete Column (2). Click to Enlarge

While working on a graduate research project during my time at the Constructed Facilities Lab at NC State, I worked on a thesis by Pablo Robalino (2). We tested lightweight concrete columns for seismic lateral forces to see flexural and shear deformation. Notice in Figure 2 how the flexural damage occurs on the side of the lateral force, while the shear damage occurs throughout the column towards the ground. The combination of these effects must be considered when designing columns for the lateral loads associated with earthquakes.

Figure 3: Column Specimen From Seismic Test

Figure 3 is a chuck of a column we tested. Notice the lines drawn with permanent marker. These lines follow cracks in the concrete caused by forces on the column. As we tracked their progression, they naturally followed similar trajectories as those depicted in Figure 2.

These aren’t difficult concepts to understand, but even with the best methods of absorbing forces, costs often limit the investment we can place in a structure to prepare for the worst. While we can’t feasibly prepare for earthquakes of every magnitude, we can use physics, properties of materials, and our growing understanding of these natural disasters to build structures capable of sustaining many of the forces that seem beyond our control.

Sources:

In other artistic news, my friend Jessica Prescott published a guest post that I wrote on her poetry blog. If you think you have what it takes to pen a magnificent six-word short story, Ernest Hemingway style, head over to the comments section and give it a shot.

It was more like a small tremor here in Raleigh. As exciting as it sounds to witness such an unusual force of nature, what’s important is that the damages were few and far between. It was felt from South Carolina to Maine, but the extent of damages occurred at the Washington National Cathedral. In fact, some very funny internet meme’s are already circulating about the quake. Important to note here that earthquakes less than a 6.0 magnitude rarely cause damages to roads, buildings, or bridges, but if there’s any doubt, structures should be evaluated.

I worked on a few earthquake simulations at the Constructed Facilities Lab at NC State. We had a shake table to use to simulate the effects of an earthquake, similar to this one. You may hear peers or even members of the media refer to the “Richter Scale.” This is wrong! The Richter Scale was abandoned years ago because of the upper limit on it’s order of magnitude and it’s unreliability at around 600km away. MMS, a similar logarithmic scale, replaced Richter. It is similarly based on orders of magnitude, i.e. a 6.0 earthquake is 10-times as strong as a 5.0 earthquake, a 7.0 10-times as strong as a 6.0, and so on, but without the inherent problems of the older method.

Recent events such as the earthquakes in Chili, Haiti, and Japan have brought Earthquake Engineering back into the spotlight. This is a very important field and one that deserves more research funding than it receives. Very rare to have an earthquake of this magnitude in this area of the United States. If you felt it, congratulations. Now get back inside and go back to work.

Went backpacking last weekend in Uwharrie National Forest. I forgot just how far twenty miles was with a pack. Talk about hot, I also forgot why I hadn’t backpacked in the beginning of August before. Made stroganoff at camp with the trusty Whisperlite, and we filtered most of our water from the streams we crossed. Looking forward to revisiting the trail in the fall when the leaves change color!

Full story: Reuters