The Importance of Multiple Data Points

Today we take up Part 2 in our discussion of work zone data. I’ve written in the past about the things we take for granted as practitioners that we should stress to others. Another of those is the importance of multiple data points within the work zone. Permanent ITS systems measure and report speeds over a segment of roadway. Bluetooth  loops, RTMS and cell phone data can all report the time it takes to drive from point A to point B. But when that number suddenly increases, none of them can tell you where the problem is located.

This also is true when evaluating work zone performance. Data supplied by permanent systems may be able to tell us average speeds and volumes, but that only indicates if there was a problem or not. It does not identify that problem.

By placing multiple sensors prior to the work zone and at key points within it, we will immediately know when the traffic slows and where the slow down begins. This has several important advantages:

  • It tells EMS where to send the responders, shortening response times.
  • It tells DOT where the problem lies in the traffic control. If it persists, they will know to make changes.
  • It usually alerts key stakeholders faster, because the system doesn’t wait until the delays reach a level sufficient to trigger an alarm. As soon as one sensor detects slow or stopped traffic, an alert is sent.
  • It helps future designers avoid similar problems.
  • It logs the incident and helps to better identify it later when matching it up with reports from law enforcement because you will have good idea of where it took place.

In short, permanent systems measure macro segment traffic flow. It gives you the “big picture”. Portable systems are much more granular and offer detail that was not available until now. This micro data is something that most DOTs don’t even know they need, until they have a chance to see it. But once they do, they wonder what they ever did without it!

The Value of Real-Time Data

Today I would like to discuss data. Everyone agrees it is important, especially in light of the focus on performance in the new highway bill. If we don’t collect data, we have no way of evaluating performance. But what data should we collect? And how can that data be used to both evaluate performance and help to improve that performance over time? We need some data now to make decisions in real time. But is that the same data we need when the project is complete and we are looking at ways we could improve next time?

This is a complex subject. Over the next few blogs we will consider three issues related to data:

1)      Data is a key product of work zone ITS. Always require access to it, in real time.

2)      Speeds over segment versus speeds at key points in work zone.

3)      What are best metrics for wz performance?

Today, we begin with data and the importance of access. Work zone ITS systems generate a large amount of data. At the top of the list is traffic speeds, counts, and volumes. There are the logs of messages displayed on each message sign and the alerts sent as emails or texts to key personnel. There are the logs showing who accessed the system and who chose to override the message sets. There are also the logs showing voltage levels and other measures of device status. This list boils down to:

1)      Work zone performance measures.

2)      System outputs.

3)      Security and system overrides.

4)      Maintenance.

When choosing to include work zone ITS in a project to mitigate traffic impacts, our goals vary but they generally fall into two categories. Our first goal is usually to maximize throughput and safety. Any other goal is going to be in support of this first goal. They will be to measure the effectiveness of the system, to collect data for use in designing future projects, etc.

Data needs are either short term or they are long term. The long term is used to look back once the project is complete to evaluate the performance of the system, evaluate the other work zone traffic control or staging, or other uses that are non time sensitive. There are also a wide variety of short term needs.

The most important of these is “feel”. By digging into the data you get a feel for the location, time of day and duration of traffic “events”.  That makes it far easier to make effective adjustments in staging or traffic control.

Feel also helps you to eliminate false alarms and/or verify all alarms were legitimate. Once you check several low speed alerts, you will know they are accurate. If they are not you will know which sensor locations should be adjusted to avoid false alarms from slow moving construction equipment or other anomalies.

Raw data helps you adjust alarm parameters until only the true emergencies are treated as such. Agencies always set the trip speeds high to begin with, then slowly reduce them until they are comfortable.

Access to real time data allows agency and contractor personnel to get their hands dirty. They can drill down into the data and get a better feel of how the system works. This will result in more effective use of the system on the current project and on future projects.

This is only possible when you have real time access to the data driving the system. So be sure to specify it the next time you include work zone ITS in a project.