Report from the Automated Vehicles Symposium

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The annual Automated Vehicles Symposium was held again this week in San Francisco. Attendance continues to grow in this TRB sponsored event, topping more than 1500 manufacturers, academics, and other practitioners.

Breakout Session #18 was titled, “Reading the Road Ahead: Infrastructure Readiness.” As the name implies, this session focused on our roads and what must be done to prepare them for autonomous vehicles.

The first section looked at the State of Machine Vision Systems. Both speakers: Jaap Vreeswijk of MAP Traffic Management and Tom Alkim of the Dutch Road Authority talked about results in Europe. They both pointed out road conditions vary from facility to facility and even from one section to another. And for that reason they suggested that a system should be developed to tell drivers what level of automation is supported as conditions change.

This would also apply to temporary changes such as work zones. As autonomous vehicles approach a work zone the driver would be told to take control as a work zone is just ahead. Once through the work zone, the driver could return control to the vehicle so long as that road segment supported it.

The actual mechanics for this process was not discussed. Digital maps could notify us of upcoming changes in the roadway requiring more or less human control. But it could only do so for work zones under 2 possible scenarios: 1) if a local device was placed in advance of the work zone to send out a signal to approaching traffic, or 2) if maps are continuously updated with real-time information…in other words if they have perfect knowledge of all work zones.

That was the subject discussed later in a session developed by Ross Sheckler of iCone. I was asked to deliver that presentation and it was well received. Ross pointed out both the need to place work zones on the digital map, and the fact it can be done today. We are already sharing real time work zone locations and related data with services including Waze and HERE. But we could do so much more if we can just get more sensors out into devices like arrow boards or flagger paddles.

Once we have enough of these in service, motorists and traffic management centers will both come to depend on this accurate, real-time data. And safety will be much improved when even utility workers appear automatically on the map when they turn on their flashing lights.

Combining Queue Warning with Dynamic Late Merge

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In our last post we talked about the ATSSA “Tuesday Topics” webinar held June 27th. Joe Jeffrey began the webinar with a discussion of work zone ITS basics. Chris Brookes of Michigan DOT shared some of his lessons learned. The final speaker that day was Ross Sheckler of iCone there to talk about coming trends in work zone ITS. Ross declared that the next big thing will be queue warning combined with dynamic late merge.

Mr. Sheckler began by looking at the state of our industry. He said that nationally there are nearly 1,000 deployments per year now. Costs of these systems are dramatically lower than they once were. And the economy and simplicity of these systems have not affected their flexibility. In fact, because applications vary, flexibility always has been and always will be an important feature of work zone ITS.

And for that reason it is very easy to add features, including dynamic late merge. As Ross pointed out, queue warning systems have their limitations. When volumes increase and queue lengths extend beyond the limits of a queue warning system additional steps should be taken. By instructing drivers to stay in their lanes and take turns at the merge point, it reduces the overall queue length, makes the best use of limited capacity, reduces road rage, and sometimes can even improve throughout.

In his drawings of typical system configurations he listed 4 sensors and 1 portable changeable message sign (PCMS) for queue warning. For queue warning with dynamic late merge he added a second PCMS at the merge point to tell drivers to take turns and a fifth sensor to narrow the gap between sensors midway through the affected area. So, in total, just 1 more sensor and 1 more sign. This is a minimal added cost and significantly increases the capabilities of the system.

The message here is that we can often solve multiple problems with one system. It just takes a slightly different logic in the controlling software. In this case you can solve problems with end of queue crashes and conflicts at the merge point with one inexpensive, easy to use system. So please remember this the next time you specify a work zone ITS system. Consider all of the challenges you face on that project, and think about ways work zone ITS may mitigate one, two or perhaps even many of them.

This webinar covered a lot of ground in a very short time.  It was recorded and can be viewed by ATSSA members anytime at: http://www.atssa.com/TuesdayTopics/Recorded. Or watch for possible future webinars on this same topic.

 

Work Zone ITS Lessons Learned

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On Tuesday, June 27th the American Traffic Safety Services Association (ATSSA) presented another in a series of “Tuesday Topics” webinars. This one was on Work Zone ITS. These are meant to be short (30 minutes) to fit into everyone’s busy schedules. I spoke first on the basics of work zone ITS. I talked about components, software, and how they were all combined in the field to form different types of systems.

After that introduction Chris Brookes of Michigan DOT discussed some of his lessons learned. He had several interesting points I would like to share with you today. Most of them concerned portable changeable message signs (PCMS). Work zone ITS systems collect data, analyze it, and trigger events but the most important thing these systems do is trigger preprogrammed messages on PCMS. That is the primary way in which these systems affect driver behavior.

His first lesson learned was the importance of using multiple message signs on both the shoulder and median sides of the freeway, especially where you have heavy truck traffic. Shortly after one of his first system deployments, he drove the job to see how it was working and had to call the office because he never saw the message sign. It was on the shoulder next to an on-ramp where trucks were entering the freeway. As a result Chris, and probably everyone else, never saw it. He recommended putting out several signs to be sure the message is seen.

He recommended using portable transverse rumbles trips just before the message signs to wake drivers up so they pay attention to the message on the signs. He said they have found that was especially effective and got far better results than the signs alone did.

Mr. Brookes talked about message construction for queue warning. Message signs well in advance of the slow down should display something like SLOW TRAFFIC / 2 MILES AHEAD. But signs closer to the slow down, especially less than a mile away should not be so specific because queue lengths ebb and flow. For those nearby signs he recommended a message like WATCH FOR BACKUPS.

The one topic that was not focused specifically on message signs was contract language. Chris suggested separate pay items for sensors, message signs, cameras, etc. He said you often get started on a project and find you need additional devices. And by including specific pay items, it makes it fast and easy to add more later on.

There were more questions at the end of this session about his next point than any other. Chris Brookes recommended blanking the message signs when traffic was in free flow conditions. He feels that drivers, especially commuters, who pass the signs regularly will quickly learn to ignore generic messages. But when they pass a sign that is normally blank and now is displaying a message, they will probably pay attention.

This runs contrary to current trends. State DOTs are being pressed by their governors to display something on permanent CMS to demonstrate to drivers that their tax dollars are being used wisely. But it would be a mistake to apply this policy to work zone ITS. These systems are there to reduce crashes in work zones. And we agree with Chris that by displaying messages only when conditions justify it, we will get better results.

This was a short but very effective webinar. It was recorded and can be viewed by ATSSA members anytime at: http://www.atssa.com/TuesdayTopics/Recorded. Or watch for possible future webinars on this same topic.

Variable Speed Limit Systems – Revisited

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In a post on April 24th we discussed a recent webinar on variable speed limit signs. The speakers voiced their disappointment in the technology and found very little if any benefit from their use. But now a new study by the University of Missouri saw far better results for VSL signs used in work zones.

“Evaluation of Variable Advisory Speed Limits in Congested Work Zones” by Praveen Edara, Carlos Sun and Yi Hou found far better, but still mixed results when using Variable Advisory Speed Limit signs in work zones.

As we have known for some time, the VSL results depend to a great extent on the algorithm used. In the Missouri study the original algorithm used in the field resulted in shorter queue lengths and reduced speed differentials. In fact the maximum speed differential was reduced by a remarkable 10 MPH. However it also reduced throughput by 7 to 11% and travel time increased by 4 to 8%. So the results were mixed.

They then experimented through simulation. Using the same traffic data they tried two other algorithms. One smoothed over a one minute period and the other over a 5 minute period. The original field algorithm smoothed over a 30 second period.

The 5 minute smoothing algorithm still reduced throughput but only by about 1%. At the same time it reduced end of queue conflicts by 30% and lane changing conflicts by 20%. Speed variances remained low. And they saw medium to high compliance with these advisory signs.

Compliance is key, of course, and the Missouri experience was very different from previous installations in places such as Utah and Oregon. Even where VSL posted limits were enforceable, compliance only occurred when message signs explained the reason for the speed limit reduction or when law enforcement was present and actively enforcing those limits.

The reasons for this could be many. Maybe Missouri drivers are just more law abiding. It was not discussed in the study but perhaps MoDOT did a better job of explaining VSLs to the public before they were installed. Or perhaps the need for variable limits is more apparent to drivers in a congested urban work zone. But whatever the reason, it is clear we should not give up on variable speed limit systems just yet. More studies are needed, especially on the subject of the best applications for these systems and the algorithms driving them.

Innovate.ATSSA.com

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As most readers will know, I’ve been involved in work zone ITS for nearly 20 years now. So I assume most people are aware of the technology and aware of the availability of studies, best practices, specifications, and more. But one should never assume, especially in a discipline where new practitioners are arriving every day.

This was hammered home to me in a phone conversation yesterday. A fellow contractor complained about a state that just let a project with a work zone ITS spec that no one can meet. Another person on the call told a similar story about an engineering firm.

This is compounded by the fact that those not in our industry don’t know where to begin their research. For that reason the American Traffic Safety Services Association (ATSSA) has created the “go-to” website for work zone ITS. You will find it within their Innovate.ATSSA.com website at: http://innovate.atssa.com/work-zone-its.html

This website was just introduced to members in February. It is still new so we are adding resources every day. But because it is new, you can be sure that everything there is current and the best information available.

On the ATSSA website you can learn about new technology, you can search for projects by state, and you can view upcoming industry events where you’ll be able to learn more. There is a blog area where you can read this and many other work zone ITS – related blogs. And most important there is a large section devoted to news and resources. Check it out today!

Google Maps are Wrong!

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At any given time, perhaps 5% of Google Maps data is wrong. And the reason is simple. Construction traffic control requires contractors to close lanes, redirect traffic into oncoming lanes, or close roads altogether until the work has been completed. Those closures are reported to state and local agencies. And those reports are picked up by Google and other traffic data aggregators. But they are often wrong or out of date.

In most states, contractors are required to request permission to close a lane. That request must be made well in advance of the date on which they wish to close the lane, 7 to 10 days on average. By the time that day comes long, construction delays, weather, and other issues often postpone the work and the lane closure does not take place.

Contractors also often make several requests so they will have a multi-day window in which they can perform the work. The days they don’t work are called ghost closures. Some states have moved to eliminate ghost closures by requiring contractors to call the local traffic management center when the lane is taken and again when it is opened back up. This certainly helps, but it does not eliminate the problem altogether.

To make matters worse, many closures are never reported at all. Utility companies are notorious for closing lanes without permission. They reason that they are only there for a short time and so won’t affect traffic all that much. But as traffic becomes more dependent on accurate travel time and route information, any disruption causes problems, and may even be dangerous.

Incident response closes lanes; school crossing guards stop traffic; special events close roads and reroute traffic; flooding, fires and other environmental events also result in route closures and restrictions.

This is an important point of discussion in the automated/autonomous vehicle world, too. If autonomous vehicles depend on historic GPS data to plan and drive a route, they will run into unexpected construction. So they must decide how they will adapt to changes in geometry, in the number and location of lanes, and much more. And delays resulting from these closed lanes and detours should be measured and included in any travel time algorithms.

It is worth noting that the folks in the traffic data companies know of the problem but they can’t solve it on their own. Industry is beginning to fill this need. Arrow boards and flagger stop/slow paddles are being reinvented to become “smart devices”. They report in automatically when work begins and ends. And they also report their precise location. As the work moves, that is reported as well, so map data for work zones can now be reported in real time.

Much work remains to be done. But the solution to this problem is clear. The closures must be reported in real time from the field. And that includes any changes in geometry when lanes are temporarily shifted in one direction or another. Highway construction, incident response and special events all experience unexpected changes on a daily and often hourly basis. Maps must reflect those changes if our system is to be as safe and efficient as possible.

Variable Speed Limit Webinar

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Variable speed limits systems have always, at least intuitively, promised benefits for work zones including greater throughput, reduced speed variance, and as a result, fewer crashes. We discussed these systems in a post in October 2015 after a presentation at the National Rural ITS meeting in Utah. The concept made sense and we looked forward to greater use of VSL systems.

A webinar was just offered April 4th by the US DOT Office of Assistant Secretary for Research & Technology entitled, “Variable Speed Limit Systems – Are They For Everyone?” The speakers, and there were several of them, did a great job of explaining the advantages and disadvantages of these systems. Those speakers included Jimmy Chu of FHWA, John McClellan of MnDOT, Bryan Katz of Toxcel, Jiaqi Ma of Leidos, and Vinh Dang of WsDOT.

There wasn’t a lot of new information. Instead they presented a comprehensive history of VSL systems from around the country. They looked at different uses for these systems, including work zones. In all, more than a dozen different projects from 9 different states were discussed. Some projects were relatively small, and others like those in Minneapolis and Seattle, were quite large.

But in almost every case, the results of these systems have not met expectations.  This was true for weather related systems, work zones, and congestion management applications. Reductions in speed variance and crashes were very small if not non-existent. And the reason in every case was a lack of conformance by the traveling public. There was some smoothing, but very little.

Many of the system designers anticipated this and included variable message signs alongside the VSL signs to explain why the speed reduction was justified. But drivers either misunderstood when they were supposed to slow or simply chose to continue at their current speed until they saw the problem for themselves.

Law enforcement is critical for these installations. Without enforcement, compliance will never reach levels that will result in the benefits designers expected. But law enforcement often became distrustful of the data they received, or didn’t get timely notifications at all. They also ran into serious resistance from the courts. So enforcement slowed, and compliance tanked.

There is still hope that these issues will one day be resolved. But for now, variable speed limit systems just aren’t providing the benefits we all hoped to see.  The webinar closed with a short discussion of future considerations. One thought was to combine these systems with a larger big data process (as discussed in our last post). They might look at not just weather, or work zone conditions, but also at traffic speed and volume data approaching the area, timing of major events, and more to improve drivers trust of VSLs.

Another thought was with regard to automated vehicles. Will VSL systems be more effective when the information is sent directly to each vehicle? If a pop-up display recommends slowing to 35, will they be more likely to do so? Or will they continue to ignore them as they apparently do now? Once autonomous (driverless) cars are on the road, the recommendations from these systems will be adopted automatically. But until then, compliance will remain the biggest problem for VSLs.