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.

Automated Vehicle Roundtable Held at ATSSA Midyear Meetings

The American Traffic Safety Services Association (ATSSA) recently concluded their annual Midyear meetings in Williamsburg, Virginia. Their Innovation Council met on August 23rd. But before the meeting began officially, they held a joint round-table discussion with members of the Automotive Safety Council. The ASC represents manufacturers of automotive safety system components including cameras, LIDAR, radar and other sensors.

The ASC led off by presenting a sort of Automotive Sensors 101 class that explained the different technologies, what they do well, and what they don’t do so well. This was a big help to ATSSA members who must design traffic control devices that these sensors will be able to “see” and react to in the very near future.

Cameras used for lane tracking look out about 500 feet on highways with a viewing angle of 40 to as much as 100 degrees. The viewing distance decreases on city streets while the viewing angle increases. As camera technology improves, they plan to hold the lane keeping range to 150m as there is little benefit to extending it. Instead they will widen the field of view to better detect pedestrians, balls rolling into the street, etc.

Cameras currently see black & white (gray scale) and red. White lane markings are much easier for cameras to see than yellow because white has far better contrast.

The ASC maintained (as we do) that digital maps must be updated in real time. Long term work zones are easy enough to include in digital maps. Short term work zones are more of a problem. And chip seals are the worst as they are short term AND include no pavement markings – just chip seal markers.

As we move from level 3 to 4 and 5 automotive system hardware won’t change much. It will probably decrease in price, but that’s all. Rather the system functionality and human-machine language will be the key differentiators. The algorithms used by the vehicle to decide what is important, what is not, and how the vehicle should react will constantly evolve and improve.

The ASC shared their market forecast for growth in the next few years. In 2020 the first level 5 vehicles will be sold. Level 2 (driver assist) vehicles will total about 13 million vehicles. By 2030 more than 90 million vehicles will have at least level 2 automation and level 5 will total nearly 3 million vehicles. But that means less than 5% of all vehicles on the road in 2030 will be level 5.

There are still very different approaches to level 3 automation. At level 3, vehicles will automatically center in their lanes, follow a route and stop when required. But unexpected conditions, such as work zones, causes the vehicle to return control to the driver. Some manufacturers see level 3 as a step toward levels 4 and 5. But others, especially Google, feel level 3 is dangerous and so will not produce cars requiring human control at any time. Level 3 peaks in 2025 at 2 million vehicles then drops as level 4 and 5 vehicles become more popular and available.

The ASC group told us control will be ceded in work zones. But how that will happen is not clear. Still, they agreed with us on the need for sufficient time for the driver to acclimate before having to make important decisions.

Once the ASC concluded their presentation, Scott McCanna of David Evans & Associates made a presentation from our industry perspective and asked several thought-provoking questions about work zones along the way.

When channelizing devices including cones, drums and delineators are used to redefine a lane, will device spacing become important for automated vehicles? Will we need to maintain some minimal spacing to hold CAVs attention? And what happens when one or two cones are knocked down? Will the automated vehicle become disoriented? Or revert to the old lane markings?

It was further suggested than CAV logic should see drums and cones as a higher priority when choosing a direction of travel than existing pavement markings. Drums, cones, etc. should indicate a change…perhaps one that automatically triggers driver control in the case of Level 3 CAVs.

The time went by very quickly and everyone agreed it was a great first step in building better understanding between our two industries. Future meetings are already planned to build on this and plan for our future.

 

National Dialogue on Highway Automation

Being the work zone data nerds that we are, we attended the National Dialogue on Highway Automation Workshop #2: Digital Infrastructure and Data held August 1st and 2nd in Seattle. The first workshop covered planning and policy. Workshop #3 focuses on freight. #4 is Operations and is held at the same time as the National Rural ITS meeting in Phoenix. The final workshop will be held late this year in Austin and will be more technical in nature as it covers infrastructure design and safety.

Each workshop includes a series of presentations followed by breakout groups where ideas are discussed and then shared with the larger group. The format works well and benefits from the input of a wide range of stakeholders.

You will be happy to hear that work zones came up early and often. In fact the opening comments used work zones as an example of the need for some sort of standardization as every agency now provides varying amounts of data, different types of data, different formats and a very wide range of detail. Another speaker called work zones the “low hanging fruit” for highway automation in general and data collection and dissemination in particular.

There were about 200 in attendance and maybe 30 raised their hands when asked who attended the Automated Vehicle Symposium last month in San Francisco. So, this was an almost entirely new group.

You should also know the FHWA is seriously committed to this process. They had 20 or 30 of their own people at this event running it, moderating the breakout sessions, and asking lots of questions.

There were a number of themes that jumped out at us. One was data quality and verification. The consensus was that state DOTs will probably have the responsibility of verifying data accuracy. But what that process might be is unclear. It will likely vary by data type. In our case it will probably come as a quality check after it is already posted. Work zone activity must be reported in real time to be actionable, so they will weed the inaccurate reports (and reporters) out after the fact.

Remarkably most in the room were well acquainted with the MUTCD. Multiple comments suggested that it needs to be revised to recognize automated vehicles. Some even suggested reducing the leeway states have in specifying sign formats, pavement marking details, etc. to create more consistent traffic control for CAVs. But later others pointed out this is unlikely to happen and the effort would be better spent doing this outside the MUTCD process, at least to begin with.

These two days were time well spent. If you are able, we strongly encourage you to participate in one of their future workshops, especially the event in Phoenix. It will be focused on traffic operations. But because it will be held in conjunction with the NRITS show, it will also spend more time on automated vehicles and rural roads.  Learn more HERE.

News from the Automated Vehicles Symposium

We just returned from the Automated Vehicle Symposium held annually in San Francisco. It has always been a wonderful venue for the exchange of ideas and concerns about automated vehicles. This year work zones and roadway safety infrastructure continue to make progress in the AV world. In fact, it is remarkable how the conversation has changed in a few short years. Three years ago, we told the automakers what they needed to understand about work zones. It was a major epiphany for them. Last year we offered a way to report work zones in real time. This year the discussion focused on the tools available and how best to use them.

Breakout Session # 32 titled “OEM/DOT Dialog on Dedicated Lanes, Work Zones, and Shared Data” was broken into those three topics. They were all worthwhile but in the interest of time we will focus on the work zone portion here. The focus of the session was real-time reporting of work zones to automated vehicles and digital maps.

Ross Sheckler of iCone started off by describing the tools that will make work zone reporting automatic and accurate – both in terms of location and time.

Paul Pisano of FHWA discussed the connected work zone grant. They are evaluating in-car traffic information. The study runs from May 2017 to March 2019. One of the desired outcomes of the study is to standardize work zone data elements. Every state, every practitioner, etc. has their own list and they have started the discussion of what should be on that list and how it should be formatted so that everyone can report things like work zones in the same way.

They plan to do this in two states: what they called a low-fidelity version and a high-fidelity version. The Low fidelity version will come first and includes the simplest of elements: GPS location, start and end dates, and some description of the work zone such as “right lane closed”. The later, high fidelity version will include detailed lane level mapping and much more.

Bob Brydia of TTI discussed his work with connected work zones on I-35 between Austin and Dallas. He collected data on each and every lane closure – 1,000s of them over the past few years. Each recorded lane closure included 60 fields to describe each closure. That’s a lot! But OEMs have told him they want much, much more!

In a related topic it was pointed out that in the recent federal RFI on connected vehicles, two different US automaker trade associations said they want a universal work zone database! So, we all see the need. Its just a matter of deciding what it should include, as Paul described earlier.

Bob Brydia says they currently send work zone data out as traffic info to help drivers. But eventually this will become more of a traffic operations function. CAVs will use this info to automatically reduce delays and speed travel times.

It was a great session, as always, and we look forward to more dramatic progress next year.

 

FHWA’s National Dialogue on Highway Automation

Many thanks to Brian Watson of the American Traffic Safety Services Association for his recent email regarding the FHWA’s efforts to get road users involved in a discussion of the impacts and issues surrounding automated and autonomous vehicles. This is an important opportunity for those of us in work zone ITS to get involved. For that reason we have reprinted his email here:

I recently attended a webinar on the FHWA’s National Dialogue on Highway Automation. I have attached the link to the recorded session, and a background on the FHWA program below. Please note the five automation focus areas include many of the aspects of our industry. If you have any questions, or would like to get involved please let me know. The next meeting will take place in Detroit at ITS America in two weeks.

https://ops.fhwa.dot.gov/automationdialogue/index.htm

Background

Automated vehicles have the potential to significantly transform the nation’s roadways. They offer potential benefits in safety but also introduce uncertainty for the agencies responsible for the planning, design, construction, operation, and maintenance of the roadway infrastructure. The Federal Highway Administration (FHWA) is initiating a national conversation with partners and stakeholders to better understand the implications of highway automation to facilitate innovation and inform the Agency’s role in this area. This National Dialogue on Highway Automation represents a series of meetings held across the country to facilitate information sharing, identify key issues and prepare the infrastructure and the broader transportation community to safely and efficiently integrate automated vehicles into the road network. Input received during the National Dialogue will help inform national research, policy, and programs and will aid in the development of a national transportation community for automation.

This National Dialogue will engage an expanded set of stakeholders, beyond FHWA’s typical stakeholders, in order to ensure that this issue has broad input. These stakeholders will include but is not limited to original equipment manufacturers (OEMs), technology suppliers, transportation network companies (TNCs), associations, and public-sector partners.

The meetings will be held in different locations across the country, running from June 2018 through the end of 2018. These meetings will be conducted as 1 to 1.5 day events and generally include 100 to 150 participants. These meetings are meant to gather input and information from stakeholders and will include significant interactive components, such as breakout discussions and listening sessions.

Automation Focus Areas

  1. Planning and Policy: This focus area will explore relevant issues for the planning and policy community, such as travel demand changes from automation, land use implications, infrastructure funding, right of way use, transportation systems management and operations, automation legislation/policy and other topics.
  2. Digital Infrastructure and Data: This focus area will center on the data requirements and needs of automated vehicles (e.g., digital work zone maps, road closures, etc.). It will explore the possibility of developing new partnerships and collaboration between public agencies and industry for data sharing and safety.
  3. Freight: This focus area will deal with truck platooning applications and automated truck freight delivery issues. It will cover possible implications on traffic patterns and operations, as well as potential infrastructure considerations.
  4. Operations: This focus area will survey the range of operations challenges from highway automation and initiate a discussion on what further research is necessary to address them. These challenges may include incident management and system inefficiency which may have implications on traffic patterns and roadway capacity.
  5. Multimodal Safety and Infrastructure Design: This focus area will cover infrastructure requirements, standardization, and consistency for automation. It will highlight topics where automation technology developers and public agencies need collaboration to plan for locations where existing roadway infrastructure, road conditions, design features and environments could lead to potential safety hazards.

Autonomous Navigation Challenges, Part 2

In our last post we looked at the current state of the art in autonomous vehicle navigation. Another way in which the problem of navigation in unmapped or incorrectly mapped areas will be overcome is through artificial intelligence. We looked at the potential of this technology in our 4/10/17 post entitled, “Machine Learning and Work Zones”. Michael Reser published an article May 8th in Electronic Design entitled, “How AI Will Help Pave the Way to Autonomous Driving”.

Mr. Reser’s main point is that given the unfathomable quantity of data that must be digested and acted upon by autonomous vehicles (AVs) the technology will progress much faster and more accurately through machine learning. “Translating it all into a real-world challenge for AI-backed autonomous-driving systems, the expected outcome of such massive data processing is nothing short of getting the right answer in the shortest possible time to determine a proper action to avoid a traffic incident.”

“To put it differently, (a) large set of data in combination with realistic scenarios and nonlinear parameter sets enables systems and applications to fail safely and learn faster.”

He goes on to list the many challenges that must also be addressed including how to tie images from multiple sensors with varying resolution quality into one accurate picture. Another was how to validate and tie different data sources together in time. They must have a consistent way of labeling those sources in time.

Mr. Reser goes on to say they are not there yet, but he sees the process as inevitable.

“For true enablement of Level 4 and Level 5 automated driving, the system should be functional in all weather and driving conditions, which is obviously a given requirement. Still, it’s a much bigger challenge than sometimes mentioned and admitted”.

Like most AV challenges, this one has serious implications for work zones. It will be interesting to watch as this process unfolds.