INRIX, a company that provides real time traffic information to mobile phones, gps, maping services etc…, has released a report of the worst traffic in the US. Los Angeles, New York and Chicago are the top three most congested metro areas. They also make up 23 of the top 25 worst bottlenecks.

Not surprisingly for the most part the larger the metro area the worse the traffic. My own metro area, San Antonio, is 28th in size and 26th in worst traffic. Though, there are a few that don’t. Austin is 37th in population but is listed as 21st on the worst traffic list. Looks like opportunities for traffic engineers.

Check out the list and other reports at http://scorecard.inrix.com/scorecard/

There are a lot of different branches of civil engineering.  I’m going to go over a few of them for those of you that are new to the industry.  That will give you an idea of what you can focus in and what you may want to do after you graduate.  Today I’ll talk about traffic engineering and what traffic engineers do.  Or more specifically I’ll make a list with bullets.  Us engineers seem to like lists.

Definition
The Institute of Transportation Engineers (ITE) defines traffic engineering as “that phase of engineering which deals with the planning, geometric design and traffic operations of roads, streets and highways…their networks, terminals, abutting lands and relationships with other modes of transportation…for the achievement of safe, efficient and convenient movement of persons and goods.”  Basically traffic engineers make the transportation work.

Some Examples of What They Do
Coordinate signal lights so that you don’t have to stop at as many red lights
Do studies to determine speed limits
Do studies to determine the need to traffic signals, stop signs and other traffic controls
Develop systems to move traffic efficiently through high traffic areas like schools, sporting events and rush hour traffic

Major concerns
Efficiency – getting people where they want to be as fast as possible
Safety – getting them there safely
Economics – doing it for a reasonable cost

Resources
AASHTO A Policy on Geometric Design of Highways and Streets (Green Book)
FHWA Manual on Uniform Traffic Control Devices (MUTCD)
TRB Highway Capacity Manual

Design Software Used
Tru-Traffic TS/PP – www.tsppd.com
Synchro – www.trafficware.com
PASSER – ttisoftware.tamu.edu

Links For More Info
www.ite.org
www.ite.org/pdf/trafeng.PDF
www.fhwa.dot.gov
www.transportation.org
www.trb.org

There are some quick notes and links to much more information.  What are some important things that I should add to this list?

It’s always important to tryout new technology. But keep in mind the benefits of old technology. And never underestimate the ability of someone to not do the right thing. Here’s an article about how LED signals at a signalized intersection may have been a contributing factor in a collision.

Did Oswego driver die due to LED signals?

What happened is that the city replaced the old style bulbs in the traffic signals with LEDs. On a snowy day in April the signal was completely covered in snow. Traffic on the main street continued to go because they couldn’t see that the light turned red. Traffic on the side road went when their light turned green. They were hit by the main street traffic.

According to the article, since regular bulbs get hot they melt the snow. LEDs don’t get very warm so the snow didn’t melt. Because of situations like this, us engineers will be asked to develop solutions so that it doesn’t happen again.

I, like most of you probably did, learned that if a traffic signal is out, then you should treat it like a four way stop. Whether you believe the accident is the fault of the city for not making the signal clear or the fault of the driver for driving through without being able to see a green light, this is one example of why we design the way we do.

What do you think? Whose fault is it? What could we, as engineers, do to make sure it doesn’t happen again?

I’m going to make a couple of points today. First of all, when you are new to civil engineering and first learning to calculate things like concrete columns and roadway curves, it can seem like everything that is in the real world is over designed. There are many rules and regulations that must be followed in your designs. My second point is about engineering ethics. All of the rules can’t cover everything.

Tacoma Narrows Bridge

Every civil engineering student gets to see the one of the videos of the Tacoma Narrows bridge collapse. I was shown this video in three or four different classes in school. If you haven’t seen the video here’s one I found on YouTube. This one is in color and has some additional information.

As far as I’ve been able to find out, the engineers followed the standard rules of the day. By their calculations the bridge should have been fine. But it wasn’t. It collapsed four months after being finished. The engineers fail to account for wind. In a lot of ways, because of this bridge, we have to take into account aerodynamics when designing virtually any structure. Not just aerodynamics, though, we as engineers need to take into account every potential source of forces that may affect our structures.

I 35W Bridge

Here’s a video of the I 35W bridge collapse in Minnesota. This bridge had held well for many years. The initial design could handle the current expected loads. However, later engineers didn’t fully account for additional loads from improvements to the bridge. Specifically, it appears that the gusset plates didn’t have a large enough safety factor. More information on the cause can be found in this article about the University of Minnesota’s Independent Study. According to the study, in addition to the gussets and later improvements, temperature changes played a large role in the collapse. These kinds of things should be considered in an original design. They also need to be double checked when making improvements.

Cypress Street Viaduct
This third video has two parts. One is about the Cypress Street Viaduct and the other about a dam at a coal mine. The Cypress Street Viaduct is another bridge that collapsed due to greater than expected forces. In this case an earthquake. The bridge was designed to easily handle the vertical loads, however they didn’t account for the lateral loads caused by an earthquake. They really only considered enough lateral load to handle wind.

All three of these videos show reasons that we have some of the design standards that we do. We have to include all of the forces that will act on the structure. Not only the everyday forces, but also expected maximum forces. Then we add a safety factor on top of that to take into account anything we didn’t think of.

The second half of that last video adds something else to this. The dam collapsed even though engineers at the time knew how to construct a safe dam. At the time, however, there were no regulations on this type of dam. To save money no engineering was actually done, and no standard maintenance or construction standards were followed. This resulted in the dam collapsing. What this means to us as engineers is that even if there isn’t a law saying that we have to do something a certain way, we should still do it the right way.

Engineering ethics is extremely important to civil engineers. This is one of the few industries where people can get seriously hurt or killed if we don’t do things the right way. Because of that, follow the law and approved standards. If they don’t provide enough guidance then use your engineering judgment and the experience of experts to do the right thing.

Have you had any experience where the standards didn’t meet the needs of you project? What kinds of things have you seen?

Porous pavements, both asphalt and concrete have been around for years.  In most areas they haven’t really caught on.  Now, with the large focus on environmental issues and green building, are they worth looking at again?

Pavement design

Traditional pavement design

Typically when pavement mixes are designed, they include different sizes of aggregate.  They use a wide range from fine sand to coarse stone.  The largest size depends on the expected use of the material.  Then it is all bound together with binder or cement.  With asphalt pavement that top layer will go on a water proof layer then a base.  Concrete pavement may go on a base or directly on the ground.

This results in an impenetrable surface that blocks rain water from getting into ground water systems and increases runoff.

Porous pavement design

Porous pavement or pervious pavement is designed using medium and large sized aggregate without any smaller fines such as sand.  It is then held together using with cement or binder.  The lack of fines in the mix creates relatively large pore space in the pavement.  This large pore space allows water to pass through.

The top layer is placed either directly on the ground or on other porous base layers to allow water to drain completely through the system into the ground.

Pros and Cons

Here are some pros and cons as well as a few notes on them.

Pros

Increased water quality – Oils, heavy metals and other contaminates on the pavements are not carried downstream and into stormwater drainage systems.  Also, water is filtered as it passes through the pavement.

Lower initial construction costs – Construction costs may be lower because porous pavements lower the amount of stormwater drainage facilities that a site will need.  Fewer and smaller inlets, detention ponds and storm drain pipes means lower construction costs.

Lower long term costs – less maintenance needed for storm drain and filtration systems.

Fewer fees – Storm water impact fees may be lower since porous pavements are proven to reduce runoff.

Less runoff – Less runoff means less potential flooding and lower peak flows.

Increased safety – Since water drains through the pavement there is a lower chance of hydroplaning and an increase in traction.

LEED Points – It can indirectly help gain LEED Points.  It can contribute in the areas of Stormwater Design, Heat Island Effect, Water Efficient Landscaping, Recycled Content, and Regional Materials.  There may be other ways that using it can help LEED certification.

Cons

Higher initial construction cost – Yes, I know I listed construction cost as a pro also.  The cost of constructing the pavement itself tends to be higher than regular pavement.

Soil restrictions – The soil below the pavement must drain at least as well as the pavement.

Clogging – The pores in the pavement may clog.  Suppliers and other proponents say that regular cleaning and maintenance will nearly eliminate clogging.

Pavement strength – Porous pavements are structurally weaker than standard pavements.   That generally results in them being used only for low traffic roads and parking lots.  Extra care must be taken when designing a pavement for high traffic or heavy traffic.

New/Untested technology – That’s not entirely accurate.  The technology has been tested since at least 1971.  However, most contractors don’t have experience with it.  Proper training, clear instructions, material testing, and site investigations should be done to ensure that the pavement meets all applicable standards during construction.

Contamination – Pavement surfaces usually have a lot of contaminates on them.  Porous pavements can filter contaminants, but no system is 100%.  Since water drains directly into ground soil it is possible that it will take the contaminants with it.

Conclusions

There is a lot of potential for porous pavements in future projects.  Each project would have to be investigated independently to determine any cost or environmental savings that might be gained by using porous pavements.  However, the potential positives do seem to outweigh the potential negatives.  It would certainly be worth your time to investigate it and present your findings to your client.

What are your thoughts on Porous and Pervious Pavements?

Some resources with additional information.

http://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Tool6_Stormwater_Practices/Infiltration%20Practice/Porous%20Pavement.htm

http://www.perviouspavement.org/

http://www.perviouspavement.org/benefits_LEEDcredit.htm

http://www.epa.gov/

Traffic jams are certainly not limited to Big City, USA.  Traffic problems are pretty much a given anywhere that lots of people live.  No matter where you live traffic engineers are constantly looking for ways to solve the problems.  Private companies are looking for ways profit by helping people through the traffic.  When you combine those efforts some interesting solutions emerge.

For example, South Africa has gridlock that can rival any American city.  To give you an idea; Johannesburg, a major city in South Africa has a population of nearly 4,000,000 people, the metro area is 10,000,000.  Pretoria, the country’s capitol, is only forty miles away and has a population of almost 2,500,000 people.

Recently engineers and private corporations have come together to develop a work around for those willing to pay a little bit.  Three companies: Cellfind, a cell phone locating company; Trafficnet, an online traffic update service; and Tracker, a vehicle locating service similar to LoJack here in the States, have developed miTraffic.  For 12 South African Rand per week, about $1.50, you can get live traffic updates.

Basically, they use the locating technology that Tracker already has in about 100,000 vehicles to determine the road they are on and the speed they are going.  Then send your cell phone the average speed on each road.  You can read an article on it called Say Goodbye to Gridlock.  Here are the links to the companies involved to read more. miTraffic Cellfind Trafficnet Tracker

Now for my two cents.

The Cons
This is certainly a bandage not a solution.
There will need to be at least one vehicle on the road that you’re interested in to get any data.
Could you save $6.00 a month by driving around traffic?
How fast exactly is it updated?

The Pros
This is a cheap possibly effective response to the problem.
The number of vehicles with tracking devices will probably consistently increase.
$6.00 a month is pretty cheap compared to the time you could save sitting in traffic.

I think the idea is a good one.  It’s a very inexpensive possible solution to the problem.  As engineers we not only need to find the best solution to a problem, we need to find a solution that is practical and cost effective.  Tearing up all of the streets and replacing them with the perfect design may be a great idea, but nobody is going to be willing to pay for that.  And nobody will want to put up with that much road construction.

We have similar technology here in the states.  However, it’s been my experience that it takes so long to update that it has never actually helped me at all.

Anybody here ever tested this system?  Know of any other systems that work well?  What about theories on things that might solve theses kinds of problems?