Motorists traveling Route 140 near Taneytown will soon be surprised to find out where the rubber meets the road: in the rubber-tire asphalt that will pave four miles of the busy highway between the Carroll County town and Westminster.
It's part of a state highway department test to find ways to dispose of growing mountains of old tires that are discarded every year. Mixing the shredded, melted rubber with asphalt and laying it on the road can solve a troublesome disposal problem and improve the durability of highway pavement. At least, that's the theory.
Marylanders discard some 4 million rubber tires each year, and 20 million of these unwanted pneumatic doughnuts are lying in illegal dumps throughout the state. They eat up valuable landfill space and they never decompose when buried, an environmental headache.
Most landfills won't even accept old tires, and the state will ban all landfills from taking tires next year. So they are tossed by the roadside or into the woods and creeks, creating another environmental eyesore and a big cleanup problem.
Through a $1 tire tax imposed last year, Maryland is starting to clean up the worst of these waste piles of tires and to underwrite research into how best to recycle these discarded rubber hoops.
Scrap tires have been used for decades in experimental mixtures to help pave roads, but the process has yet to be perfected. It's twice as costly as straight asphalt and more difficult to apply. And there are concerns about toxic fumes from the substance during the paving process.
State test strips have already been laid on Ady Road near Bel Air and Route 340 west of Catoctin Creek in Frederick County, as researchers struggle to find the best proportion and method of blending these paving substances. On the Taneytown project, engineers will use from 1 to 3 percent rubber in the asphalt, mixtures that will consume about 6,200 used tires. All told, the University of Maryland will test 24 such projects in the state.
Road pavement with added rubber seems to be more durable and more resilient, a long-term construction benefit. But the major advantage will be in finding a useful way to recycle scrap tires. That's why the federal government is proposing that 5 percent scrap-tire rubber be used in asphalt on its highway paving projects; the goal is to reach 20 percent scrap rubber in paving by 1997. It's a promising way to retire that worn out automotive footwear.