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.

The Illinois Model for Procurement of Work Zone ITS

Yesterday I had the pleasure of sitting in on yet another Smarter Work Zones webinar from the Every Day Counts folks. This was lucky number 13 in this wonderful series and looked at procurement of work zone ITS. You can download the recording in a few days at: https://www.workzonesafety.org/swz/webinars

Early in the webinar an attendee, Charles Martin, made a statement in the chat box that I thought helped focus the discussion. I believe he once worked for Maryland SHA and that experience and perspective showed through when he said, “I find that the most complicated issue to determining how to fund adding SWZ’s often it is not one project driving the need, but rather several. One may have Fed-aide, and others may not. (N)one of the projects may have funding to add ITS.”

The webinar that followed may not have answered his concerns completely, but it did offer several innovative options that should work in most situations.

Todd Peterson of FHWA began by giving an overview of procurement methods and explained that the best option depends on the type of work zone ITS you plan to use. Jerry Ullman of Texas Transportation Institute (TTI) ran through the different contracting methods that three states (Massachusetts, Texas and Iowa) have used and shared some lessons learned. Finally, Matthew Daeda of Illinois DOT went into detail on his state’s approach and that’s what we will talk about today.

Illinois uses a two level approach to procurement of work zone ITS. For larger contracts and longer term projects they try to identify the need as early in the process as possible. This is usually accomplished as a lump sum line item in the bid documents. Details regarding the types and quantities of devices are included in the special provisions. When they know they will have serious traffic impacts, they include WZITS and other mitigation strategies in the bid documents.

They will also add WZITS under change order when impacts are greater than expected. Again this is done with the same language they use when it is included in the bid.

Illinois

But for smaller projects and short duration traffic impacts, they are now using an on-call contract. Each district advertises a bid for this on-call service. Districts 1, 8 and 9 already have three year contracts in place. Districts 2, 3 and 5 have or will soon have contracts in place. Districts 4, 6 and 7 will follow suit very soon. The on-call work zone ITS is paid for using HSIP funding.

These on-call contracts are intended to provide queue warning for projects with a duration of two weeks or less. In District 1 (Chicago) and 8 (St Louis) the vendor supplies 4 changeable message signs and 4 sensors. In more rural District 9 the vendor supplies 1 changeable message sign and 4 sensors. Each district adjusts the quantities to fit the needs of that district. District 9 includes rates for monthly rentals. Districts 1 and 8 only include daily and weekly rates.

This contracting method offers several advantages:

  1. The state only pays when the system is needed.
  2. They work directly with the vendor and that greatly improves communication.
  3. Staff has direct access to the system data and to make changes.
  4. By bidding for each district local companies are more likely to win, thus reducing response time.

Mr. Daeda offered several lessons learned. He said that one vendor installed software in their TMC that did not work well with their firewall. In the future he would like to require vendors to install and test any software before getting a notice to proceed.

He would like a pay item for supplemental devices. Then he could add more sensors or message signs when they are needed.

When deployments run over a month, they currently pay for a month at the monthly rate and for additional days beyond that at higher daily and weekly rates. Mr. Daeda wants to change that going forward to be at a percentage of the monthly rate once the system has been out for more than a month.

Matthew plans to clarify language regarding relocation of devices. And there have been times when he wished he could add camera trailers.

In our last blog post, “The State of the Work Zone ITS Industry”, we talked about the many ways in which 2015 was a landmark year. This webinar is a perfect example of that. These EDC events just keep getting better. The speakers were all on topic and very professional. The webinar service worked without interruption. And the attendees asked great questions.  If you haven’t watched them yet, you are missing out on a great experience!

Jump Start Work Zone Intelligent Transportation Systems in Your State

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We just got back from ATSSA’s annual Traffic Expo held this year in New Orleans. The focus of this show, more than ever before, was innovation. There was a lot of talk about automated and autonomous vehicles. And there were two great workshops on work zone ITS. In particular, I moderated a session Monday morning entitled, “Jump Start Work Zone Intelligent Transportation Systems in Your State”.

It was very well attended, 15 state DOTs were represented along with several local agencies and contractors. The material presented was fresh, and a very lively discussion followed afterward. The workshop looked at new and innovative ways states are contracting for work zone ITS in general and queue warning systems in particular.

Jerry Ullman of TTI led off by talking about the Texas model for contracting for these systems directly with the system providers and outside of the normal project contracting process. Steve Kite of North Carolina DOT talked about his state’s plan for doing the same thing through something similar to a professional services contract.

Keith Roberts of Illinois DOT described what they have done to bid an on-demand contract in his district. They tried doing it in a couple of different but similar ways in two districts. It has been so successful that Illinois is now going state wide. Priscilla Tobias, the Illinois State Safety Engineer, has approved bidding on-demand queue warning systems for all 9 Illinois DOT districts.

The bid includes rental rates for sensors and portable changeable message signs by the day, week and month. This on-demand contract is intended to supply queue warning for projects where the traffic impacts are short term, or unexpected. It could also be used for major incidents. Large projects requiring queue warning already include these systems as a line item and won’t normally use the on-demand rentals.

The obvious advantage to this method is you only pay for the system when you need it. There is never a need to justify use of a queue warning system until the queues develop. And then you order the number of devices you need to address the problem. It really is a more economical use of funding.

Another less obvious advantage is the agency works directly with the system supplier. Communication is faster and more seamless. DOTs learn the system capabilities faster and more completely and make better use of them as a result.

Many other states are now going forward with their own on-demand contracts including Indiana, North Carolina, and Michigan. And given the number of states that attended this session, don’t be surprised if several more join them very soon.

On-demand queue warning has revolutionized work zone ITS. It makes it available when and where it is needed, not just on large projects where traffic impacts are anticipated. We all owe a large debt of gratitude to Jerry Ullman of the Texas Transportation Institute for pioneering this method and to Priscilla Tobias and Keith Roberts of Illinois DOT for perfecting it.

If you would like to learn more you can begin by downloading the Illinois District 9 specification Illinois spec.