Combining Queue Warning with Dynamic Late Merge

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: Or watch for possible future webinars on this same topic.


What Do Automated and Connected Vehicles Need to Know About Work Zones?


On July 20th, Ross Sheckler of iCone made a presentation to the Autonomous Vehicles Symposium in San Francisco. The title of his presentation was “What Do Automated and Connected Vehicles Need to Know About Work Zones?” His message was very important. It was well-received by those in attendance, but the group that needs to hear this is many times larger than the 100 or so people in the room that day. So we will try to make his main points in today’s post.

Remember, most of the attendees were not work zone people, though a few of us were there that day. Most work for automotive manufacturers or component manufacturers. They produce navigation systems – some in use today and some that will guide autonomous vehicles in the future. Those cars will drive through our work zones, yet the folks who produce them know very little about temporary traffic control. So Ross began by pointing out that the map changes 1,000 times per day due to work zones. 1,000 times per day workers change the law, and 10,000 times per day warnings are posted. His point being, of course, that we must find a way to inform these systems.

Mr. Sheckler also explained that most closures are never reported. And of those that are reported, most don’t occur on the dates and times they are scheduled. He went on to say that the most dangerous closures are probably those unreported ones. He used the example of a short term utility closure on a rural road with bad line of sight.  The people doing that type of work often do not worry much about traffic control. They might place a 10 foot taper of cones and a ROAD WORK AHEAD sign, but even that is somewhat rare. Automotive systems must be able to recognize these work areas and react appropriately.

And when traffic control is reported, it only shows up in navigation apps as “roadwork”. It does not say it is a lane shift, or multiple lane closure sure to cause queuing. It does not say the entire geometry has changed by moving traffic over into the oncoming lanes separated by concrete barrier. And it does not tell you if the work is causing traffic to slow or stop. A shoulder closure is reported the same way as a full roadway closure with detour. Yet one does not affect traffic at all while the other may affect travelers’ choice of routes.

His point is that by reporting these changes as they occur it gives drivers the opportunity to avoid the area altogether. But the information must be posted as the changes occur and it must be accurate. If it is, drivers will learn to depend on it and change their routes. But if they get erroneous or inaccurate information, they will continue to drive along their intended path.

Ross finished by listing the details that are important to navigation apps, and this applies to current apps as well as future autonomous driving systems.

  1. Work zone status: scheduled versus equipment on sight and ready to work versus workers present.
  2. Map changes including lane shifts, capacity reductions of any kind, or roads closed.
  3. Queue details including slow or stopped traffic, delay times, early or late merge systems, and location of merge point.
  4. Presence of active flagging operations including location.
  5. Presence and location of attenuator trucks, especially when the attenuator is in the down or active position.

These are all details a system will require to make informed routing recommendations. And if the work does cause significant impacts, we prefer they avoid the area altogether. It is safer and more efficient for everyone involved: travelers, contractors, and for the owner/agency.

Our industry can supply this information today. So please encourage system designers to engineer with that in mind. We can all avoid a future full of expensive, time consuming, and even dangerous problems by getting the word out now.

Lane Merge Systems

Late last year the FHWA Every Day Counts initiative held another wonderful webinar. This one covered two more work zone ITS products: variable speed limit systems and dynamic lane merge systems. You can view the recorded webinar at:

Last time we discussed portable variable speed limit systems. Today let’s discuss lane merge systems. Todd Peterson of FHWA began by explaining the basic structure and goals of a lane merge system and explained the differences between a late merge, early merge, and dynamic merge system.

Chris Brookes described Michigan DOT’s use of a late merge system. Their applications were last minute, high volume so a late merge made sense. He shared data showing remarkable reductions in queue length and delays. But he said there is a “steep learning curve.” When the local media supported their efforts with stories on the system, remarkable benefits were achieved. But when they did not run stories, those benefits disappeared. So drivers need to understand how the system works, what is expected of them, and why that will benefit everyone concerned.

Todd Peterson described a dynamic merge system in Maryland. There they saw high volumes during the day and low ones at night. So an adaptive system made more sense for them.

In both Michigan and Maryland they enjoyed several benefits as a result of these systems:
• Reduced speed differential between two open lanes in advance of the closure – Michigan had no recorded crashes when the system was in use.
• Reduced frustration by creating a sense of fairness.
• Reduced queue lengths – Michigan saw them go from 5 to 7 miles down to less than 2.
• Reduced delays – Maryland saw increased throughput of 9 to as much as 34%.

During this presentation two more questions were asked of the audience. They asked if their agency was considering using lane merge systems and about 70% of them are. They then asked if they were looking at early merge or late merge. 100% were considering late merge. There is no data to support this, but you’d have to suspect the interest is coming from agencies working in urban areas with high volumes and resulting capacity issues.

The data presented clearly shows remarkable benefits from late merge systems. Their low cost and ease of deployment make these an excellent tool. The Every Day Counts website includes lots of useful resources to help your agency get started using these systems. Check it out at .