Does Size Matter?

Today let’s talk about another important feature of today’s work zone ITS systems: scalability. This is a feature often overlooked. Industry doesn’t mention it because they take it for granted. But we should. New and potential users of our systems don’t understand how simple it is to add or subtract devices to arrive at a system scaled to fit each project.

We just finished up a short term project in Sacramento known as Fix50. It required the closing of multiple lanes on this important route through downtown. Significant queuing was expected. Instead of a typical queue warning system consisting of 4 or 5 sensors and 2 or 3 message signs, this was much larger. Queues were expected to extend at times to more than 2 or 3 miles. Furthermore, the project ran between two major interchanges and queuing was expected to back up onto those other routes.

Sensors and message signs were placed on both Hwy 50 and on the freeways that intersected with it. Drivers on Hwy 50 saw messages like SLOW TRAFFIC AHEAD, PREPARE TO STOP. Drivers on those other freeways saw messages like SLOW TRAFFIC ON EB50, PREPARE TO STOP.

Earlier this month this blog discussed a new article written by Tracy Scriba of FHWA. She wrote about the value of queue warning systems. “Using technology for queue detection and warning can be particularly effective when queues are unpredictable and therefore unexpected by drivers. When it is difficult to predict when and where queues will occur, it can be challenging and costly to use manual methods, such as to have sufficient staff available to cover extended time periods, and to keep the warning device (enforcement vehicle or truck-mounted dynamic message sign) in the proper location relative to the end of the queue.”

She went on to back this up with new data supplied by Illinois DOT: “In an analysis of queue detection and warning systems implemented at several work zones by IDOT, crash statistics from 2010 (prior to system implementation) and 2011 (after system implementation) showed nearly a 14-percent decrease in queuing crashes and an 11-percent reduction in injury crashes. These reductions occurred despite a 52-percent increase in the number of days when temporary lane closures were implemented.”

This represents a significant improvement in safety. We don’t always have before and after data we can compare, but we know queue warning systems have reduced the number of crashes on the projects that used them.

This also results in a significant improvement in system efficiency. Fewer crashes mean fewer delays. And both are true for large projects as well as smaller ones. And because these systems are scalable, the cost of a queue warning system is proportionate to the size of the project. So these benefits are available to any project, large or small, where queuing will be a problem.

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