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.