They are known by different names and are cheaper to install and more portable than concrete barriers. But over the last few years, agencies responsible for roadway maintenance have discovered a costly problem when it comes to plastic pylons. Also called delineators, channelizing devices or tubular markers, these traffic control devices offer an initial cost savings over concrete barriers. Over the long term, though, they can have a lot of unexpected costs.
Plastic pylons are those tall, thin, flexible devices used on roadsides to indicate lane edges in curves or, most often in larger cities, as a cheaper alternative to concrete barriers for lane separation in managed or HOV lanes. They started showing up on Texas roadways about 10 years ago and have grown in popularity owing to their relatively low installation costs.
“Plastic pylons have numerous advantages over concrete barriers, including costs, and they are used in a variety of applications,” Texas A&M Transportation Institute (TTI) Research Engineer Robert Benz points out. “Unfortunately, they are often hit by vehicles. They can break, and the pylons have to be replaced.” Benz learned that one Texas Department of Transportation (TxDOT) district spends around $200,000 per year replacing damaged plastic pylons.
Benz led TTI’s research team on TxDOT Project 0-6643, Guidance for Effective use of Pylons for Lane Separation on Potential Lanes and Freeway Ramps. The two-year study included a state-of-the-practice review, vendor and agency surveys, documentation of maintenance and safety experiences, pylon spacing testing and recommending guidelines for implementing pylons.
“Manufacturers offer various sizes and qualities of these plastic pylons, yet there is very little guidance on which pylons to use in which applications, or even how far they should be spaced. And that’s why this study was conducted,” Benz says.
Another study about pylons is under way at TTI’s Proving Ground facility. Researchers are currently examining pylon durability by crashing vehicles into them, over and over again, at 70 miles per hour. Engineering Research Associate Dusty Arrington prefers the more technical term delineator over pylon.
“We’ve finished the first year of this two-year study, and my hope is that it will help TxDOT determine which delineator is best used in each application, and therefore have fewer failures,” Arrington says of TxDOT Project 0-6772, Development of New Delineator Material and Impact Testing Standard to Prevent Premature Failures Specific to Installation Application.
Arrington is working to develop a complete impact-testing standard, which could eventually require each product to be tested. “You obviously don’t need the most durable delineators on roadside applications where they are seldom struck. But at the same time, the least durable delineator should not be part of an HOV lane separation,” Arrington says.
Final results and recommendations will be available following the study’s completion next year.