Sunday, September 14, 2008

Antique Craft Techniques Makes Roads Safer

The City of Clayton, MO has turned back the clock to make its streets safer for pedestrians. At crosswalks throughout the city's central business district the city is installing a three-quarter inch overlay of BrickPrint from Traffic Calming USA to slow traffic and draw attention to where pedestrians cross.

The high-tech material in BrickPrint is installed using age-old work practices reminiscent of blacksmithing. Glyn Owen, vice president of operations for Traffic Calming, described the BrickPrint material as essentially molten brick. The material includes recycled glass, sand, and 25-30 percent granite stone flecks. Special equipment heats it to 400 degrees Fahrenheit to melt it.

The key to working with BrickPrint is the same as the key to working with iron: keeping it hot enough mold into shape. The installation crew from Traffic Calming use hot spreaders - thick metal rods with flat surfaces welded onto their ends - which they warm in a heat box under the blast of a propane torch, much like a blacksmith might heat his metal before working it. One worker fills a battered bucket with the molten BrickPrint material and pours a line of it across the crosswalk. Another worker grabs a hot spreader and uses it to smooth out the material. He has scant minutes to work before the material cools too much to work with it. As soon as the spreader cools, he trades it in for another hot one. As he finishes each line of material, the guy with the bucket pours another one. A third worker throws sand across the top of the material so a fourth worker can hand stamp a brick pattern into it with metal mold.

Owen said it takes about three hours to install a complete crosswalk. The material dries in one hour and comes with a three-year guarantee.

Bob Phillips, regional sales manager for Traffic Calming USA, said the material will not delaminate as did some thinner overlays applied in St. Louis in the 1980s. Since it goes on at 400 degrees, "it melts the layer of asphalt below it and bonds to it," he said. The color is mixed throughout the material so it will not wear off.

Phillips added that the company has different formulations for different climates to better resist both cracking and softening.