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.

Is There an Ideal Sensor Location?

Are there “perfect” sensor locations? For example, when we deploy a queue warning system, are there sensor locations that will get us better data? Could that data inform us of slowing traffic sooner? Or could it be a better indication of traffic conditions than data from another location would be?

For end-of-queue warning systems we submit that the ideal sensor location is just upstream of where queuing is most likely to begin and, therefore where average speeds vary most.

There are locations like that throughout the work zone. Narrowing of lanes, lane shifts, temporary concrete barrier, bridge falsework and other construction activities affect drivers sense of safety. Anything that negatively affects that feeling of comfort will reduce the 85th percentile speed.

Short on-ramps with reduced merge distance have the same affect. However, if traffic always quickly accommodates those merges and returns to the previous 85th percentile speed, then that is not a perfect location. Only when the geometry in combination with traffic volume results in dynamic queuing does that become a good sensor location for queue warning systems.

The power source is our greatest limiting factor today.  Batteries, solar systems, etc. take up space. They must be located where we can reach them easily for maintenance. For this reason, many sensors are located on message signs and arrow boards where they can draw power from them and even share communications devices.

Arrow boards are placed at the taper. Queuing begins there, of course. But we will only catch speed variance due to conflicts at that merge point. We won’t see if that variance continues upstream.

Message signs are placed in advance of the work to warn of slowing downstream. We should always place one sensor at a point that queuing would reach as a result of a worst-case scenario. And a message sign location may be able to serve both purposes. But we normally want the sensors located where queuing begins and we want the message signs located upstream to warn of that slowing – not located together. If sensors and message signs share the same locations they are likely either too close to the work zone or too far from the source of the queuing to warn traffic before they reach the problem area.

We generally space sensors out every half mile to a mile apart with the understanding that we will learn about any queuing quickly. And that is a good approach. After all, we can’t predict all causes of queuing. But couldn’t we adjust those locations a little one way or the other to catch these obvious causes of slowing a little earlier?

It would be helpful to see research into sensor location. But in the meantime, let’s evaluate our work zones and adjust our sensor locations to monitor the more obvious sources of slowing. Our systems will perform better and improve work zone safety even more than they do today.

Final Report on Every Day Counts 3

USDOT has published their final report on the activities included in Every Day Counts 3. That included the promotion of work zone ITS. We talked about their efforts in past posts (10/27/14 and 12/14/16 ) and applauded both their efforts and the results, but now we can look at the final numbers. Read the report HERE.

When they began in January 2015 there were 7 states that had already made the use of technology to reduce work zone traffic impacts a mainstream practice. 8 more states were in the assessment stage at that time. Bu December of 2016 – just two short years later – 11 included work zone ITS as a mainstream practice and 13 more had moved to the assessment stage – a 37% increase!

More important, those efforts are already bearing fruit. Wisconsin’s initial tests indicate a significant reduction in end-of-queue crashes. They are now working with a university partner to develop a queue warning system decision support tool to help project designers know when to include a system in their jobs.

Illinois DOT has awarded on-call contracts to provide work zone ITS system in three of its districts. They, too have studied the effectiveness of these systems. Once they finalize their research they plan to incorporate that in their future system deployments.

Massachusetts DOT “uses smarter work zone technology applications in all construction work zones that meet a specific impact level and a preset scoring criteria threshold.”

And New Jersey DOT developed scoring criteria for designers to use when determining whether work zone ITS should be included in a project. Work zone ITS was also added to its preliminary engineering checklist as a tool for mitigation of work zone impacts.

Thanks again to FHWA for their foresight and hard work on this. It was just the push states needed to get started in work zone ITS and is sure to save a great many lives in the years to come!

 

The State of the Work Zone ITS Industry – 2018

We just enjoyed the 4th of July holiday. As we sat on the deck consuming bar-b-que and adult beverages we considered the state of the work zone ITS industry. We really have come a long way in the past year and that deserves recognition and a quick look back.

One of the most important and most overlooked recent changes is the blurring of the lines between the permanent ITS infrastructure world and the work zone ITS world. At last month’s ITS America show in Detroit, HERE demonstrated their new ability to incorporate live data feeds from work zones along with their partners including software provider GEWI and work zone ITS supplier iCone.

Waze is also incorporating real-time work zone data feeds in their traffic reporting. Both traffic data providers understand the importance of immediate and accurate work zone reporting and are working internally to make better use of our data.

This blurring is going the other direction as well, as Work Area Protection (formerly ASTI Transportation) now offers the option of including Iteris probe data in work zone travel and delay time calculations.

This blurring of the lines may be more important than we realize. Because it becomes less about us versus them for funding and more about an ITS system that works all of the time – especially in work zones. Work zones have always been an afterthought with ITS practitioners. But that is changing. They now understand that the single largest cause of nonrecurring congestion is work zones. And they are working to address that with their permanent systems.

In a recent article in Better Roads Magazine Frank Zucco of Wanco explained that work zone ITS is now much less expensive. Large, elaborate systems are still available and make sense for multi-year projects with major traffic impacts. But more and more simple systems are now being used for queue detection, trucks entering and dynamic merge applications. And, as Frank points out, those are now very dependable and inexpensive, making them a cost-effective solution for most projects.

Research now validates what we all knew intuitively. Queue detection, in particular, has shown major benefits according to the Texas Transportation Institute and AASHTO. We touched on this milestone two years ago in our post “The State of the Work Zone ITS Industry” published on 4/28/16.

And, lastly, work zone ITS helps facilitate the proliferation of automated and autonomous vehicles. Without real time reporting of work zones, AVs are left to navigate them on their own. And the AV world now understands that. We have become a part of the conversation. At the Automated Vehicle Symposium later this month in San Francisco sessions about work zones will be included for the third year in a row. See #33: “OEM/DOT Dialog on Dedicated Lanes, Work Zones and Shared Data” on July 11th. Autonomous vehicles are a big story that will only get bigger. Funding and research will flow to our industry as a result of these conversations.

As an industry, we aren’t yet to the point where our systems are used everywhere they could help. But we can finally see that light at the end of the tunnel.

Work Zone Traffic Control “Down-Under”

We just returned from a wonderful trip to Australia where we spoke to the Traffic Management Association of Australia (TMAA) about work zone ITS. Their members were all excited and focused on finding safer, more efficient ways to manage their work zones.

The program was packed full of interesting speakers and a variety of timely topics. They also gave us all just the right amount of time to discuss those topics between sessions. It was very well run.

The attendees seemed to enjoy talking to Americans and all asked what we thought of the meeting. My first answer was always the same: traffic control companies in both countries share the exact same set of problems:

1) Speeding in work zones.

2) End-of-queue crashes.

3) Hiring, training and retaining good employees.

4) A perception by the driving public that we are there to make their lives miserable.

5) Insufficient funding for maintenance and construction.

6) Changing standards and levels of enforcement from one state to the next.

7) Varying commitment and funding levels from one state to the next.

Just like ATSSA, the TMAA brings contractors, manufacturers, academia and government agencies together to discuss these problems and identify solutions. The TMAA does an especially good job of this. We look forward to learning more from them in the years to come!

Distracted Driving and Work Zones

We all know that distracted driving is resulting in increased fatalities on our roadways. The National Safety Council reported a 6% increase in fatalities in 2016. According to the National Work Zone Safety Information Clearinghouse, overall roadways fatalities increased 13% from 2013 to 2016. And during that same period, work zone fatalities increased 28%!

We enjoyed a period of dramatic decline in these numbers in the early 2000’s and then in 2013 they suddenly began to climb again. A small part of that change was due to improving economic activity and the increase in vehicle miles traveled that came as a result. But far more is due to other factors and distracted driving certainly tops the list.

The National Safety Council reports that 47% of drivers feel comfortable texting while they are driving. But we know that, in fact, texting while driving often increases reaction times more than driving under the influence.

But the problem is bigger than just that. In a recent article by Dr. Carl Marci, a neuroscientist writing in the January 4th issue of Perspectives magazine (http://www.nielsen.com/us/en/insights/news/2018/perspectives-driving-while-distracted-the-challenges-of-measuring-behavior-in-complex-environments.html), he said that our cars may be contributing to the distracted driving problem as well! This question occurred to him driving home one night so he ran a test using standard bio-metric equipment on a short drive on an unfamiliar road in Boston. The results showed the driver looked at his or her phone 60 times during a ten minute trip! A study by Zendrive reinforces these findings. They found that drivers use their phones for 88% of their trips.

Dr. Marci explains this by examining the way we use our phones outside of our vehicles. Any time we are bored, we look at our phone. Sitting at home in front of the TV, standing on a street corner waiting for a bus, or sitting in slow a meeting at work – we all check our phones when we get bored. And then we are often rewarded for doing so with a response from others. Email and social media have changed the way we act in very profound and far-reaching ways. And that can’t be turned off when we get behind the wheel.

Furthermore, our cars are becoming very comfortable. They resemble our living rooms more every day. Elaborate electronics help guide us to our destination, provide entertainment, and interface with our phones calling and communications applications.

We do use our cars electronics and phones for legitimate reasons while driving. They give us directions to our destination. They warn us of traffic problems along our planned route. They tell us of weather changes that may be important. So our phones & automotive electronics can help us get where we are going more safely. But once we use these for legitimate reasons, we can’t put them down. Or our drive becomes boring or our phone beeps to announce a new text, and we can’t seem to wait until we stop to check those messages.

So, back to work zones. A 28% increase in work zone fatalities cannot be ignored. Distracted driving is a growing and potentially catastrophic trend for work zones. Work zone ITS has always helped to reduce crashes. But this trend in distracted driving makes the use of work zone ITS all the more important. End of queue systems, dynamic merge systems, and variable speed limit systems can all get drivers attention, improve their work zone awareness, and help mitigate the effects of distracted driving. Let’s get ahead of this trend now before it gets any worse.

The Importance of Crash Modification Factors to Work Zone ITS

A webinar was held December 5th on work zone crash data collection and analysis. It was organized by Wayne State University and included speakers from the University of Missouri and Michigan State University. A recording of the webinar will be made available soon.

Several very good resources were made available as the webinar began including “A Guide for Work Zone Crash Data Collection, Reporting, and Analysis” which was produced for the FHWA by the Wayne State University College of Engineering. This guide can be found at:  https://www.workzonesafety.org/files/documents/training/fhwa_wz_grant/wsu_wz_data_collection_guide.pdf

As a work zone ITS practitioner, I have deployed many systems over the years but have very little data to prove the effectiveness of those deployments. The problem has always been establishing a base line of the probable number of crashes given the traffic control, project duration, traffic volumes, etc. Only with that base line can we compare our actual crash numbers to determine whether the system was cost-effective.

The crash data guide states the problem very succinctly, “In order to perform an effective work zone safety analysis, the appropriate work zone crash data needs to be available. The availability of this data is only as good as what is collected on the state crash report form.”

The webinar pointed to several states’ best practices in this regard. At a minimum, states are required to include a checkbox on their form to indicate if the crash was work zone related. But states including Connecticut, Iowa, Minnesota, Pennsylvania and Virginia collect much more. They go into detail about the location of the crash within the work zone, and what types of traffic control and construction activity was in place at the time of that crash.

That data will help them develop Crash Modification Factors (CFMs) for different traffic control treatments. In time we hope to see CFMs for queue warning systems, dynamic merge systems, variable speed limit systems, and much more. Those CFMs could be specific to high volume multi-lane facilities, rural four lane highways, etc.

Once CFMs are developed, the rest of the process is fairly simple. Compare the CFM associated with your proposed system to the traffic volumes where that system will be used, and you will know immediately whether the use of that system is justified. The use of these systems is already taking off, but there is still some guess work involved in the decision to use or not use work zone ITS. By developing CFMs we could speed that process along and make it more scientific.