In FY04, the Texas Department of Transportation (TxDOT) received a grant from the Recycled Materials Resource Center, located at the University of New Hampshire, to study the use of anti-vegetation tiles made of tire crumb rubber to control vegetation around sign or guardrail posts. TxDOT’s Recycling and Recycled Products Program, as the principal investigator, will study:

  • the ease of installation
  • the efficiencies and economics of using tiles versus concrete mow strips
  • cost comparisons of installing tiles to string-trimming or herbicide use
  • the potential life-span of the tiles for long term use

The Vegetation Control Problem

Vegetation establishment is a very important final component to new roadside construction. Without proper vegetation growth, erosion becomes a very serious problem for highway shoulders and slopes.

Once vegetation is established, however, the problem of vegetation control becomes the priority issue. As grasses, flowers, and other vegetation are freely growing along highway right-of-ways (ROW), state DOTs have found that the most effective means of vegetation control involves a combination of mowing, herbicide applications, and vegetation inhibitors.

While mowing is the most commonly applied means of vegetation control, it too can be a problem as mowers attempt to get as close to roadway signs as possible when mowing in the ROW. Often, trying to get as close as possible to reduce the amount of hand grass-trimming with a weed-eater, mowers either cause the sign to lean or damage it in such a way that requires adjustment or replacement. Application of herbicides or construction of concrete pads around signposts to restrict vegetation growth have been used in the past but can have their own disadvantages – unsightliness (herbicides) and/or expensive (concrete pads). Using anti-vegetation tiles or signpost rings offers several major advantages such as:

  • cost effectiveness (minimizes labor and material costs)
  • appearance (see photos below)
  • use of an abundant and problematic recycled material (scrap tire crumb rubber)
  • environmental (no emissions from string-trimming and less herbicide use)

The Scrap Tire Problem in Texas and the Nation

Scrap tire management is a challenge worldwide. Texas generates approximately 24 million tires annually, roughly one per person per year. At the end of 2002, an additional 66 million shredded tires were stockpiled at current and formerly registered storage sites throughout the state, plus an estimated 4.4 million whole tires remain at known illegal tire dumps. Nationwide, approximately 225 million tires are generated annually with approximately 700-800 million tires stockpiled at registered storage sites throughout the nation.

Road construction end uses can, and should, be part of the scrap tire solution – whether in the form of crumb rubber or tire shreds – and can yield engineering benefits and a positive life-cycle cost-benefit ratio in certain highway construction projects. During the past ten years, TxDOT has consumed the equivalent of more than ten million tires in asphalt rubber hot mix, crack seals, shred seals, embankment fill, and miscellaneous products made from crumb rubber.

Although TxDOT frequently purchases rubber or die-cut products for weighting bases on traffic cones, delineator posts, barrels, and other traffic control devices, TxDOT continues to explore other innovative uses of crumb rubber products, such as the use being explored by this project.

About the Primary Demonstration Project

Additional Demonstration Project – Guardrail Tiles

Additional Demonstration Project – A/V Poured in Place – Guardrail Installation

Additional Demonstration Project – A/V Tiles around Airport Lighting Units