Americans are prodigious drivers. each year, the country’s wheels spin across 1.5 trillion kilometers of roadways. That’s about 5,000 km for each man, woman and child in the United States. But despite the national appetite for blacktop, pavement rarely gets a second thought. Except when it’s time to swerve around a pothole, or bump across a rut-filled intersection. Then, chances are, the irate driver will indignantly demand, “Why don’t they fix these darn roads?”
Relax, they are.
All over the country, on quiet rural lanes and congested turnpikes, highway engineers are rolling out a powerful new principle for road building known as Superpave.
Superpave is a novel way to design hot mix asphalt, the gooey-when-hot mixture of tar-colored cement and crushed stone that makes up 94 percent of U.S. pavements. “It’s an outstanding technology,” says Neil Hawks, director of special programs at the Transportation Research Board (TRB) in Washington D.C. It’s also a big change for the largely empirical art of road building. Superpave replaces “recipe” construction, based on past experience, with pavement designs rooted in a more analytical assessment of road materials’ engineering properties. Superpave’s goal: to dress the nation’s arteries in long-lasting, custom-tailored pavements.
The new system was developed in university and industry labs during an intense, one-of-a-kind research push funded by Congress in 1987. Like any laboratory technique destined for use in the real world, Superpave has taken its lumps on the way. It’s had to take on powerful industries and it has meant a steep learning curve for the local transportation departments and contractors that actually pay for, and build, new roads. In 1996, they used the system in just 95 paving jobs. But this year, Superpave has taken flight, with the number jumping to 1,339 nationwide, accounting for nearly 30 percent of the pavement laid down in the United States.
Superpaved roads don’t look any different from their empirical counterparts. But researchers predict they will last far longer, perhaps 15 years instead of 10, before needing a major maintenance job. That should save highway departments more than half a billion dollars a year, according to an estimate from the Texas Transportation Institute. More to the point for American travelers, the study figured Superpave will save another $2 billion by saving time-fewer car repairs and fewer minutes stuck behind maintenance crews.
Superpave’s origins lie in a time when disco was king, the nation’s best-selling car was an Oldsmobile, and new road projects suddenly, and mysteriously, began failing. “There had always been cases where things went wrong and people couldn’t explain it,” says Damian Kulash, president of Washington, D.C.’s Eno Transportation Foundation. “But people started to feel it was becoming much more common.” Roads were developing the signs of old age well before their time: trough-like ruts from traffic on hot days and cracks from cold weather.
There were no clear causes. Contractors were using road-building recipes that had changed little since 1872, when New York City’s Fifth Avenue welcomed the nation’s first asphalt pavements. True, traffic loads had been swelling steadily. And heavier trucks with stiffer tires were suspected of committing dastardly acts of wear and tear. Others pointed fingers at asphalt itself, a sticky residue of oil refining. The OPEC oil embargo had reshuffled supply lines, and the nature of the material had changed.
Although asphalt had been in use for thousands of years (the ancient Egyptians used it for mummification) and gravel even longer, pavement’s mechanical properties lay largely unexplored. So when the roads started failing, highway engineers didn’t know what to change. Nor were easy answers likely to emerge from the research pipeline, which had long been dry. The numbers in a gloomy 1984 report from the TRB said it all. The semiconductor industry was spending 8 percent of sales on R&D; the pharmaceutical industry 6 percent; even R&D laggards such as the food and beverage industry ranked just shy of 1 percent. The highway industry had been spending less than 0.2 percent.
The specter of infrastructure decay and the grim funding scenario spurred Congress to action. In 1987, it kicked off the Strategic Highway Research Program (SHRP), a $150 million bid to find solutions to highway engineers’ toughest troubles. Fully $50 million went to solving the pavement problem.