Thinking Highways Article

In the current issue (Vol 7 No 3) of Thinking Highways, Bob McQueen wrote about “the readiness of the ITS industry to cope with the impending flood of new data.” He makes an important point. Agencies and suppliers must come to grips with the sheer volume of this impending flood of data and how to make the best use of it. This is as true for work zone systems as it is for every other ITS system. This is data that most agencies have not had before. They often won’t know how to use it until they have taken the time to understand what it means to their operations. Certainly the more open the data source and the more standardized we can make the format, the better it will be for everyone.

Work Zone Data, Part 3

This is Part 3 in our discussion of work zone data. In Part 1 we discussed the value of real-time data and the information available when agencies dig into that data to better understand what it is telling them. In Part 2 we discussed the value of “micro” speed and volume data at several points throughout the work zone, rather than just speed and volumes over a road segment. Today let’s talk about work zone data as a measure of performance. What metrics are most valuable when we look back over the duration of the project? What tells us if it worked well? What data best points out any problems with the design, installation or maintenance?

We also need to evaluate the work zone ITS system, itself. How can we show if it paid to have it there? Did it reduce delays? Did it improve throughput?

And, finally, we need data that is easy to collect, easy to save, and easy to compare with other projects over time. How does that affect our choices, if at all? Can we, as an industry, settle on a standard measures that everyone understands? Or does this have to be done on a state by state or even region by region basis?

In our post entitled, “Work Zone Performance Measures” dated 10/5/12 we reviewed the new FHWA document “A Primer on Work Zone Safety and Mobility Performance Measurement” by Jerry Ullman and Tim Lomax of Texas Transportation Institute (TTI) and Tracy Scriba of FHWA. This wonderful booklet did a great job of explaining the issues surrounding work zone performance measures and it shared some important lessons learned. Two of them of interest in this discussion are:

  • Focus on project level data (as opposed to agency/program level).
  • The best measures will vary widely from project to project depending on the goals of the deployment.

So we have discussed this for the past six years and now it is time to choose. I will offer my suggestions. I will list only on those measures that can be collected using work zone ITS. There are many others that should also be used including number of crashes, citations issued, customer complaints, etc. And I will break them into two groups: those I would always use, and those I might use in certain circumstances.

Measures for use on ALL projects:
  • Average speeds
  • Number of incidents (defined as anything that results in average speeds below XX MPH).

 

Measures for use on SOME projects: When this condition is present:
  • Delay time
Commuter traffic with good alternate routes.
  • Travel time
Through traffic with good alternate routes.
  • Queue length
Incentives/disincentives for maximum length.
  • Speed variance
Measure need for law enforcement.
  • Volumes
When 511 system uses it in calculations.
  • Reduction in volume through project
When good alternate routes exist.

 

So there is my list. All of these metrics would help measure the performance of our work zones. Delay time and reductions in crashes would help establish the cost/benefit ratio for the system. Please do your best to tear it apart. Seriously! Click on the comment button below and tell us what you think.

And one more question: is there data we don’t have that we wish we could collect? For example, is a reduction in speed for a period of time a good indicator of an incident? Or would some other data be better?