Common Mistakes in Work Zone ITS Lessons Learned During 20 Years in This Field

Today, we would like to discuss common mistakes agencies make when including work zone ITS in a project. But we don’t want to scare anyone away or make this more difficult than it really is. Today, work zone ITS is easy to use, easy to contract, and easy to evaluate. So please dive in and learn your own lessons as you go along.

But with that said, there are a few bits of advice we can offer from our many years deploying these systems.

The first is simple enough. Before you specify a system in a project, identify and clearly state your agency’s goal for that system. Is it end-of-queue crash reduction? Is it diverting traffic onto alternate routes? Is it speed reduction? You and every other decision maker in your agency need to agree on the primary goal, and then communicate that goal to the system supplier through your specifications.

Second, don’t try to do too much with your system. Focus on that primary goal first. If the system supplied can also handle additional responsibilities, then add those that help you meet any secondary goals. For example, a queue detection system can also provide traffic data to meet the Federal Work Zone Safety & Mobility rule. But don’t add features that will just bombard you with data you can’t use. You will have plenty to work with as it is.

Once you have your goal for the project, you can begin designing your system. If the goal is reducing rear-end crashes in slow and stopped traffic, doplar radar is the best sensor to use. It works well at low speeds and is inexpensive. But if your goal is to replace a permanent system that measures speeds, counts and classifications, a side-fire radar such as Wavetronix or RTMS.

Next choose your sensor locations. For most systems you will space them about three-quarters of a mile apart. You may get away with as much as a mile or more in some situations, but more often you will want them between a half-mile and a mile apart. Once they are in place and collecting data, check that data to be sure it is what you need. Locations with a lot of concrete barrier sometimes result in radar echo giving you false results. Locations such as a gore point at the on-ramp from a truck scales will result in below-average speeds as trucks slowly speed up onto the mainline.

Budgets often force you to limit the scope of your system. If it comes down to a choice between cameras or more sensors, please consider maximizing the number of sensors. Better, richer data will result in a more responsive system, and one less susceptible to service interruptions. If you must have cameras, limit their use and the video frame-rate to keep your wireless expenses lower.

Your specifications should include the type and quantity of sensors, message signs, camera trailers and other devices. And consider including a line item for each type of device. In that way, you will have a price if you find you need to increase or decrease the quantity of devices.

Finally, dig into your data. Learn what makes the system work. When an incident happens, look at the data to learn how quickly it affected traffic upstream. And how quickly it clears once the cause has been corrected. This will give you a better sense of the capabilities of these systems and how best to use them on future projects.

Mitigating Work Zone Safety and Mobility Challenges Through ITS – Part 2

In our last post we reviewed “Mitigating Work Zone Safety and Mobility Challenges Through ITS” (Report # FHWA-HOP-14-007) and looked at the use of “commercial off-the-shelf” systems to mitigate work zone traffic impacts. Queue systems are the most common example. But these systems also include travel time, dynamic merge and trucks entering/exiting systems.

This report also compared these with the use of custom systems and the use of permanent ITS either alone or supplemented with portable devices. As work zone ITS becomes more “plug & play” this will become much easier to do. And as it becomes easier, it also becomes the more cost effective option.

First, let’s consider off-the-shelf versus custom systems. A few short years ago all systems were, in effect, custom systems. But as time went on, common applications emerged. Dynamic merge was probably the first off-the-shelf system. This morphed into a queue warning system a short time later. Clearly, if a standard system does what you need it to do, there is no reason to consider custom systems.

But when you need something a little different, a custom system is still a good option. This study uses as an example a work zone delay performance measurement system. They used a variety of sensors to measure performance in real time and to provide that information to the DOT and the contractor.

The cost of a custom system is based on the complexity of the system, the time needed to integrate non-standard devices, and the follow up testing. They can be expensive but often these changes can be made quickly and easily. It just depends on what you are trying to accomplish. There are at least two things to consider: 1) once you have a concept of operations, try to get multiple proposals. Every system has underlying design features that help or hinder adaptation to your special application. You will find that one is probably much better suited than the others. 2) Focus your efforts and the system design on your primary goals for the project. Don’t try to do too much. Costs increase sharply with complexity while the likelihood of success falls.

Permanent ITS can sometimes give you all you need to monitor and mitigate work zone impacts. Cameras, sensors and dynamic message signs are often located in and around work zones, especially in urban areas. But two conditions must be met for them to be used for a work zone: 1) They must remain operational throughout the project. Sensors, in particular, can be a problem, and 2) they must be located at advantageous locations. A message board in the middle of the job isn’t much use in warning drivers about delays.

The use of permanent systems also depends on the goals of the deployment. If your goal is to reduce end of queue crashes, you will need sensors spaced close together. Most portable systems space sensors no more than a mile apart and often as little as a half mile apart to recognize queuing quickly and warn drivers upstream. There are locations with that number of side fire radar sensors, but they are rare.

The sensor network used for work zone impact mitigation must also fit the work zone. Much has been written recently about the use of cell phone travel time data but, at least for now, that data looks at road segments that only occasionally match up with work zones. You can monitor travel time through a corridor, but you won’t know where in that corridor (and work zone) a problem has developed.

This does not make these permanent devices useless. As this study points out, combinations of permanent and temporary devices can be used in combination to meet your requirements. It’s simply a matter of understanding the advantages and disadvantages of each.

Mitigating Work Zone Safety and Mobility Challenges Through ITS

We love studies in this business. And we have been conducting them on the subject of work zone ITS for some time now. But FHWA published another last January that deserves mention. “Mitigating Work Zone Safety and Mobility Challenges Through Intelligent Transportation Systems” (Report # FHWA-HOP-14-007) touches on several areas I would like to mention here.

This report was written by Jerry Ullman of TTI and Jeremy Schroeder of Battelle. They include several different case studies and draw lessons from each one. But first they talk about work zone ITS in general and point out that, “work zone ITS is now evolving from being an developmental strategy for improving safety, operations, and productivity to more of a “mainstream” tool available to the work zone planner/designer and developers of transportation management plans (TMPs) to mitigate specific safety and mobility challenges that can exist on a project.” Many states still treat this technology as something new and unproven, so we are gratified to see this stated so unequivocally.

The first section looks at an off the shelf queue warning system used in two locations in Illinois. The results are startling. “A preliminary analysis of the I-70/I-57 project crash statistics from 2010 (prior to system implementation) and 2011 (after system implementation) saw nearly a 14 percent decrease in queuing crashes, and an 11 percent reduction in injury crashes, despite a 52 percent increase in the number of days when temporary lane closures were implemented in the project.” This is why any project where capacity issues or geometry will likely result in unexpected queuing, should use some form of queue warning system.

One of these projects included 20 portable cameras, while the other did not. The researchers wrote that, “Camera coverage is useful, but not necessarily essential, for a successful system – At the I-70/I-57 project, traffic cameras were not specified by IDOT but were included in the final system deployed. Both IDOT and the contractor subsequently commented that the cameras were valuable for identifying and verifying when and where traffic issues arose and quickly determining how to best respond to mitigate the issues. However, the lack of cameras on the I-57/I-64 project was never mentioned as a problem by project staff. This could be due in part to the different project lengths involved. The I-70/I-57 work zone ITS covered significantly more interstate mileage than did the I-57/I-64 project. In addition, the loss of shoulders, reduced lane widths, etc. throughout the I-70/I-57 project meant that a stall or crash anywhere within the system coverage limits was fairly likely to cause a traffic queue. Conversely, the bottleneck location at the I-57/I-64 project was constrained to right at the interchange itself, a much more concentrated location that could be reasonably inspected other ways. Consequently, camera coverage to view reasons for traffic queues that developed was considered important at the one project, but less so at the other.”

Finally, the study had some good advice on estimating delay times. “Calibrate to slightly overestimate delays – Project personnel at the I-57/I-64 project noted that they found (primarily through anecdotal conversations with friends and neighbors) that it was more acceptable to the public to slightly overestimate delays when disseminating this information, but not acceptable to underestimate delays. Consequently, calibration of the systems relative to the delays calculated and presented on the signs should ensure that the delays being presented, if in error slightly, err towards the side of overestimation.”

This study offers solid, common sense advice to anyone involved in deploying work zone ITS. We will talk more about it in our next post.

Reserve Your Airspace Now!

During the recent ATSSA Midyear meetings in Nashville, Paul Morgan of Modern Technology Solutions spoke to the ITS Council about the potential use of drones. He told a very interested audience about the wide variety of Unmanned Air Systems (UAS) . They ran from very small planes weighing a few pounds to helicopters, blimps and inflatable towers. Payloads can run as high as 28 pounds but most are much smaller.

Mr. Morgan was not there to sell these systems but to 1) offer them as a possible solution in our industry, and 2) to recommend we get involved in the discussion of future regulations.

One state, I believe it was Utah, is already experimenting with these devices equipped with high resolution cameras for accident reconstruction. Normally they tie up a lane, lanes or an entire roadway for long periods of time while photos are taken, skid marks are measured, etc. This state is using drones instead to take video which is used later for the same purpose. It is just as accurate and serves as an exact representation of the entire accident scene. It saves time, reduces delays and should also result in fewer secondary crashes.

Other possible uses include regular work zone video for posting to project web pages. It is possible such a system could be done less expensively than a series of trailer mounted cameras.

DOTs and prime contractors might use the video to document progress on a project for payment purposes or to show deadlines are (or are not) being met.

UAS could be used for a variety of applications including video, sensors, and more. Think about uses that might fit your needs and lets’ talk about them in more detail.

In the meantime, he suggested we get involved early in the efforts to regulate drone use going forward. Currently they can only be used with a special permit. But law enforcement, DOTs, agriculture, and many other groups have plans for their use in the not so distant future. That airspace will be in high demand and our industry needs to ensure access for our needs. As a result efforts are already underway to craft regulations for their use. New laws could be in place as early as 2015.

So consider ways you may want to use drones in the years to come and reserve your airspace now!

Developments in Work Zone Video

OK, it is time for a mea culpa. That’s right, write this down because I am here to apologize. In my August 27 blog entitled “Cameras or Sensors?” I took the side of sensors. I argued that sensors are much less expensive than cameras and provided far more information. To my mind that has not really changed but video has come a long way in recent years and deserves a second look.

Recently, one of the most important developments for our industry is in quality digital video recorders or DVRs. They have become relatively inexpensive yet offer an incredible amount of storage. Before these became available, you had to react to alarms (provided by sensors) when the problem occurred to view the video. You wouldn’t necessarily understand how the problem developed but at least you could see what the problem was and formulate a response. So, at that time, the value of video was more reactive.

Now you can go back in time and watch how the problem developed. What happened to cause it? Was it an errant driver? Or did traffic control contribute to the problem? In other words, you can use stored video to improve upon your traffic control. It has become proactive, rather than simply reactive.

Wireless service has become more dependable and 4G service offers good bandwidth if you need streaming video but it can be expensive. And in most cases you won’t need that. A few frames a second will provide all the real time information you need to understand what is happening in a work zone. Use the money you save to add more devices or to use these systems in additional work zones.

Another change is the variety of cameras. Most manufacturers offer good 12 volt cameras now. And you may choose from color, black & white, infrared, or some combination of all three. They run from very basic “grainy” video to high quality megapixel video. The more basic the video, the more you can store on the DVR. High quality video is great, but takes far more storage space. You must evaluate that trade-off between video quality and storage. Most DVRs will begin recording over the oldest video when it is full. So the question becomes, “When an event occurs, how soon must I download the video before it will be lost?” In most cases you can design a system with 30 days storage, giving you plenty of time to find out about a problem after the fact and still go back and view it.

Cameras now offer a few more bells and whistles that may also be of interest. They can be set to scan a work area continuously. Or they can be set to focus on a particular area during morning drive time and another area late at night. This feature might improve security where theft or vandalism is a problem. Alarms or flashing lights can even be triggered when movement is detected late at night.

This feature could also be used to leverage your work zone ITS dollars. If traffic is heavy in only one direction at a time, one camera could be used to view both directions of traffic. In the morning it could view the traffic heading into town and in the afternoon it could be set to switch automatically to the outbound direction.

Cameras can still be manipulated manually. Any time a new alignment is installed, particularly lane shifts or crossovers, you should monitor traffic through it to be sure drivers understand what is now expected of them. If they handle the change well, you can pat yourself on the back for a well designed work zone. But if problems develop, you will know you need to make adjustments.

Cameras are still several times more expensive than sensors. Sensors must provide the data backbone of any good work zone ITS system. But stored video can be another useful tool in your tool box…especially when analyzing problems and making improvements in traffic control design.

Cameras or Sensors?

I don’t claim to be an expert on this subject. In fact, I hope to learn more about it from you. But I believe that when you are budgeting your work zone ITS, you are almost always better off putting most of the money into sensors rather than cameras. You only need so many cameras and you probably don’t need any at all. But I’m not sure you can have too many sensors.

In my experience, cameras cost at least three times more than sensors. The device itself is more expensive because it needs a larger trailer, more solar and batteries to power it, and a taller tower. It also costs more for wireless service because it requires much more bandwidth and it requires it continuously, not just for short packets of data. In some cases cameras cost more than 5 times as much as sensors. So, for your money, you can get three to five more sensors for every camera you give up.

We need to better understand both tools before we can discuss the budget. When do we need cameras? Most of the time cameras are used to verify the data from the sensors. Is traffic really stopped? Or was this a false reading? But if you have enough sensors, the ones on either side of the one you are verifying will quickly do it for you. And, they will do that automatically. Just because we can check the data obsessively doesn’t make it a good idea.

But this is not to say we never need cameras. There are some good reasons to have them:

  • Publishing video to a webpage helps drivers check conditions quickly and raises public awareness about the work zone.
  • Emergency response may be improved by viewing the incident first to know just how bad it really is and to direct responders to it in the most efficient way.
  • Some DOTs may want a video record of the work zone traffic control. This is still controversial but whether you agree with the idea or not, it is still a legitimate reason for cameras.

A reason that is less legitimate is the use of cameras to look at ongoing work or to look at locations on the jobsite without having to drive there. This does save time and money, but not enough in itself to justify the cost.

These are some of the questions you should ask yourself when evaluating the need for cameras:

  • Are there permanent cameras at or near the project that can be used?
  • Is the job several miles long? The longer the project, the more important video becomes to groups like emergency response.
  • Will there be several stages to the work? As construction progresses and traffic control is changed, it is important for drivers to know about those changes in advance.
  • Is public outreach a part of your TMP strategy? If so, a web page with video might be an important tool.
  • Will there be lane shifts, narrow lanes, or a significant reduction in capacity during construction? Any of these conditions may result in an increase in collisions. The more problems you expect, the easier it is to justify the expense of cameras.
  • Is this what FHWA calls a “major” project? The larger and more complicated the job, the more likely you are to benefit from CCTV.

Cameras have their uses. But next time you are planning a job, please ask yourself these questions and consider your goals for work zone ITS before you decide to add them to the project. You may be able to do the same thing more efficiently by just using sensors. What do you think? Have I left out important questions? Is there a side to this I have not considered? Make your comments now and keep the discussion going!