Improving the Effectiveness of Smart Work Zone Technologies, Part 1

illinoisstudyA brilliant study was published in November by the Illinois Center for Transportation Studies entitled “Improving the Effectiveness of Smart Work Zone Technologies.” The principal researchers were Yanning Li, Juan Carlos Martinez Mori and Daniel Work. Download it here.

It is brilliant for a couple of reasons. It moves past the studies we conduct over and over again that look at the effectiveness of smart work zone systems. Those have been done, and there really isn’t much more to be learned from additional studies. We know they work. It has been proven. Enough said.

Instead, this study looks at ways of making something good, even better. There is so much new information is this study that we will discuss it in two separate blog posts. This first one will look at their conclusions regarding sensor types, sensor spacing, and missing data. The second will consider travel time estimation and, in particular, their recommendation of the Kalmar filter algorithm.

Let’s begin with sensor types. The study focuses primarily on doplar and side-fire (RTMS) sensors.  They compared the advantages and disadvantages of each and concluded that for most work zones systems there is no advantage to RTMS type sensors. The RTMS provide more accurate flow measurements than radar due to fewer occlusion issues. But they do cost more and are more difficult and time-consuming to set-up and configure. They wrote the, “analysis indicates the types of sensors do not have significant influence of the performance of existing smart work zone systems. It is suggested the choice of sensor types should depend on the specific requirements and constraints in each work zone.”

They went on to say that given the extra cost of RTMS, you are normally better off spending that money on additional doplar sensors, as more sensors improve the data quality far more than the sensor type. Of course, if lane by lane counts and classifications are needed to meet the deployment goals, RTMS is the only practical solution.

Next they discussed sensor spacing. Most of us in the work zone ITS industry suggest sensor spacing of between 1 mile and one-half mile apart. This study confirms what we learned through experience. They said the closer you place your sensors to each other, the better the data quality. “When more sensors are deployed, the systems provide faster notification of changes of the traffic conditions and increase the estimation accuracy of the traffic conditions.”

However, anything closer than a half mile apart provides negligible additional benefits. “When the sensor spacing is smaller than 0.5 mile, the benefit of additional sensors … is marginal.”

A third topic they covered was missing data records. This has not been covered in any detailed way in previous studies. But it is important. They studied only two projects but for those projects found they were missing as much as 10% of the data records. They did point out that the system messages continued to be sent to the message signs. But what if the interruption was sufficient to delay those messages?

One vendor suggested the data records were missed due to the cellular carrier dropping them in favor of voice transmissions. If true, this underlines the need for redundant communications. Satellite backup or better cell service is a must. If data is dropped for more than a few seconds it could affect the timeliness of warnings to traffic upstream. And if that data will also be used for work zone performance measurement, it causes additional problems. A measure of system data transmission performance should be included in the evaluation of every work zone ITS deployment.

So, in short, simple systems with more sensors are better than more complicated ones.

Spacing of a half to one mile is best. Anything greater quickly loses accuracy and anything less is not cost-effective.

And agencies should require a data transmission reliability report to be sure that most of it is getting through, even during major incidents.

In a future post we will return to this study to examine algorithms, especially for travel time systems. In the meantime, download this important study!

A tale of two smart work zones

Please welcome back JP Story as our guest blogger today!

How Kansas DOT got a better smart work zone for an order of magnitude less money

The Department of Transportation in Kansas let two smart work zones in 2016. One which you’d call “typical” and one that was very different. In this post we look at how changing your approach to smart work zones can be a net positive for your state.

The number one reason more work zones are not smart work zones is because they are expensive.

According to the district engineer, Southern Illinois spent an average of $640,000 per smart work zone in 2014/2015.

If a smart work zone costs between half a million and million dollars, its no wonder more states don’t do it. It’s no wonder states are hesitant to specify them in on more projects. And it is certainly no wonder why every work zones isn’t a smart work zone…at least at those kinds of prices.

It was the same in Kansas, earlier this year. There was a letting on February 17th of 2016, a 20 million dollar project that would have a major impact on traffic in Wichita. Five bridges would be rehabbed along I-235, the major ring road of the city, and preliminary analysis suggested that significant queues would form. To mitigate risk of rear end collisions, and to help inform the motorists of delays, they included a smart work zone with end of queue warning and travel time automation.

As expected, the price came in at between half a million and a million dollars. The deployment (lump sum) at $570,000 and maintenance of $146 (each day of the project). What they got for that is 15 sensors, 10 signs, and 5 cameras. For logic, they got a travel time and queue warning system. Seems like your typical kind of smart work zone.

The thing is, it doesn’t take ripping apart and replacing five bridges to impact traffic. Sometimes working on just one bridge can have a negative impact. Let me introduce to you the 119th Street bridge in Kansas City.

Seems like a real run of the mill quick project, anticipated to last no longer than 3 months. The low bid for the project was awarded to Pci Roads for $420,106.66. Let me emphasize this fact, the entire project cost less than a typical smart work zone. Ask anyone in Kansas City, US-69 is terribly congested with commuter traffic, on a good day. Traffic analysis told KDOT that this bridge work would lead to terrible backups. But how on earth can you put a smart work zone on a project when the total cost of the project is under half a million dollars?

Kansas DOT reached out to us and wanted to turn smart work zones on their head. They saw the trend of half+ million dollar projects and wanted to do something different. We advised them on the same things we wrote about earlier this week, that smart work zones are easy.

  • Any PCMS can be a “Smart” PCMS. Let the local guys place their own signs.
  • Use your permanent infrastructure. AKA use what you already have.
  • Use what is safe.
  • Get innovative with how you pay for it.
Use Local

To recap, PCMS are commodity hardware. A “smart board” PCMS is simply a sign with a modem on it for remote communications. Nothing more. You know what you already pay for these signs – just look at your past bid tabulations. That is what we did in Kansas and came up with a very accurate estimate of the signs. Traffic control companies all have message boards already – there’s no need to bring in any kind of “special” message board. They own, maintain, and setup these message boards every day.

Use what you have

We utilized the permanent KCScout sensors in the area to reduce the sensor cost. The data flows freely to our server and we use it in the calculations to automate the message boards. Its a one-time integration that took about a week. After that there is zero cost. Many states and counties already have some traffic sensors used for traffic studies – those too can be put to work on a smart work zone, saving you tens of thousands of dollars.

Use what is safe.

There’s no need to place obstacles in the lead up to your work zone. We used break-away posts that are crash tested to mount our sensors. Oftentimes you can mount them on the posts for advanced warning signs that would be there any ways for the normal maintenance of traffic!

Re-think your payment model

We’ve seen what the low-bid process leads to when it comes to smart work zone “packages”. A half million dollar “thing” that is hard to quantify and even harder to justify for anything but the most major of projects. We want to change that. To that end, we recommend you use the low-bid process on commodity items like PCMS, and have the contractor place them. It works great. For the non-commodity items, like the traffic sensors, you can utilize the micro-payments route for sole-sourcing a competent vendor. And the same goes for the software that ties all the disparate pieces together into a cohesive system.

All said and done.

KDOT maximized efficiency on this smart work zone by implementing the above measures. The results were drastic. The bid tabulations of the 119th Street Bridge project tell the story. A $58,500 lump sum deployment vs a $570,000 deployment for the 5 Bridges “typical” smart work zone. It is also cheaper to maintain for the contractor, so the each-day payment for upkeep was only $130 each day vs $146. By changing their approach, and partnering with a software vendor on the front end, KDOT achieved an order of magnitude cost savings on this project. A partnership can leads to a very different, much better working relationship versus the low-bid environment. Is this what you want from your next smart work zone? Give us a call today if you’d like to learn more.