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.

Alternative Funding for Work Zone ITS Fact Sheet

Nearly everyone who understands work zone ITS knows it is a cost-effective way of mitigating the traffic impacts of major and sometimes even minor road construction projects. Studies have proven the value of these systems. But DOTs will often tell you they don’t have the funding to pay for it.  The FHWA encourages states to use work zone ITS. They will pay for these systems through conventional construction funding. So, when states say they don’t have the funding they mean they haven’t found a pot of money outside of the money they use for asphalt and concrete.

FHWA wants to address that problem. They have just published the “Alternative Funding for Work Zone ITS Fact Sheet”. In it they document how Illinois uses HSIP funds to pay for Work Zone ITS. Download a copy of the fact sheet HERE.

FHWA says this is a highly underutilized funding mechanism. According to the fact sheet, “While some states use HSIP funds for work zone purposes, many state DOTs do not tap into this resource. Out of the more than 4,000 HSIP projects referenced in the 2016 HSIP National Summary Report, only 13 were work zone-related projects.”

Work Zone ITS Blog addressed the efforts of Matthew Daeda and Illinois DOT on May 12, 2016. We told you that this contracting method offers several advantages:

  1. The state only pays when the system is needed.
  2. They work directly with the vendor and that greatly improves communication.
  3. Staff has direct access to the system data and to make changes.
  4. By bidding for each district local companies are more likely to win, thus reducing response time.

 

This fact sheet is a BIG deal! States are always saying they don’t have the funding. This is one way of getting it. And the Feds aren’t just allowing this. They are encouraging states to use HSIP funds for work zone ITS.

States do need to identify work zone safety as a SHSP Focus Area and provide the data to support that decision. According to the National Work Zone Safety Information Clearinghouse, there were 799 fatalities in US work zones in 2017, up from the previous three-year average of 764. That’s not much when compared to the total roadway fatalities of 37,133.

But work zones are always a safety issue. States can and should include them in their Strategic Highway Safety Plans (SHSP) for a variety of reasons. Work zones force drivers to process more information and react faster than they normally do outside of work zones. That’s why crashes attributable to distracted driving, speeding, aggressive driving, and impaired driving often show up first in work zones. Furthermore, solutions that work in work zones may have applications elsewhere.

In 2017 overall fatalities declined nationally while work zone fatalities increased. Any state with this same disparity should include work zones in the SHSP. Many states have recently increased funding for road construction. They, too, will unfortunately see an associated increase in work zone fatalities. And, again, they to should include work zones in their SHSPs.

This is a wonderful tool. Thank you to Todd Peterson and Jawad Paracha for putting it together. Now we all just need to get his in front of the decision makers in our states!

 

How Does the Traffic Message Channel Work?

We’ve talked in the past about the need to update the work zone information on digital maps in real time. But how does that process actually work? The answer is surprisingly simple while offering far more detail than you might expect. It is sent over FM radio and satellite channels using RDS-TMC protocols. RDS stands for “radio data system”. TMC stands for “traffic message channel”.

The information is sent in very small packages several times a second within a frequency used for digital identification of the station, song titles, etc. In this way, location codes and event codes are sent without interrupting the audio and updates any navigation devices in very near real time. That information can then be used in calculating the fastest route. It will also recalculate as incidents occur that cause significant delays.

In the United States the digitally coded traffic updates are distributed by Navteq over FM channels and by Sirius/XM satellite radio. iHeartMedia and TeleAtlas also provide commercial services in about 77 US metro areas.

Once received, the codes are automatically displayed in the driver’s preferred language making them more readily understandable and therefore more effective.

Each incident is digitally coded and sent as a TMC message. Each message consists of an event code, location code, expected incident duration, and other pertinent details. The message includes one or more phrases describing the problem. The first portion states the problem and the second portion gives clarification regarding the types of vehicles affected, recommended actions by the motorist, etc.

As you might expect, there are many work zone related messages. In fact, there are more than 150 work zone specific messages as well as many hundreds of messages just focused on queue length, travel delays, and lane closures. The work zone messages get fairly specific: mentioning pavement marking, resurfacing, bridge work, water main work, etc. They even mention temporary signals in one.

There are also many messages about incidents, weather, and special events.

The RDS-TMC system was developed before wide-spread use of GPS. So, they do not use a lat and long to identify the location. Instead location is described in relation to major intersections and points of interest.

As work zone reporting becomes more sophisticated, codes can still be added to provide additional detail such as the lanes that are closed, the length of the closure, expected delays, and more. Only a little more than half of the code capacity has been used so far. So there is plenty of room to grow. And that is important. Because autonomous vehicles will require far more detail. Discussions are already underway regarding what new details must be included and the formatting, etc. for them.