The Pavement Problem
Today’s interstate highways are built according to a well-established procedure. Typically, a gravel subbase is first covered with concrete. Then an asphalt mixture is applied and compacted; or, for concrete highways, a steel mesh is laid on to help absorb stresses from expansion and contraction, and a layer of concrete is poured on top. These basic materials and methods have been in widespread use for decades.
At the turn of the century, though, much less was known about paving materials. Before the automobile era most roads, if they were paved at all, had a surface of macadam (compacted stones bound with clay) or gravel. These were fine for horses and iron-wheeled wagons—if it didn’t rain too much—but when cars started whizzing along at twenty miles per hour on pneumatic tires, the roads were quickly torn to shreds. Local authorities had to improvise and experiment.
Even before the automobile many different paving methods had been tried. Cobblestones were the principal urban pavement until mid-century, but animal wastes, garbage, and diseases collected on its uneven surface. Woodblock paving seemed an attractive idea in lumber-rich areas, but it absorbed water and less pleasant liquids, grew fungi, and usually had to be replaced within five years. Granite proved quite durable but also quite expensive; sandstone was cheaper but tended to wear smooth and slippery, especially when wet. Iron blocks were tried on New York City’s Cortlandt Street, but they were noisy, and hexagonal projections intended to lend traction turned out to be too effective, causing horses to trip and stumble. Even glass blocks were installed, in Lyon, France, but they chipped and split under heavy traffic.
Brick roads were first introduced in the United States in 1870 in Charleston, West Virginia, and became quite popular over the next several decades. They were attractive, offered a good foothold for horses, and were easily repaired and cleaned. They were expensive to build, however, and the rumble they produced when an automobile drove over them was deemed unacceptable. In 1881 London surfaced two roadways with an inch-thick layer of rubber; it was quiet and easy to clean, but again too costly for general use. In the same city ground cork embedded in asphalt was tried near hospitals, where quiet was necessary; it passed all the tests except durability.
Road builders often turned to local industries in their search for auto-worthy pavements. In Newton, Massachusetts, in 1908 the newly created U.S. Office of Public Roads tried a covering made from blackstrap molasses and quicklime in a petroleum binder. It held up well under traffic but proved to be, as one reporter put it, “somewhat soluble in water.”
Other cheap and plentiful local materials that were tried and found wanting as pavement included seashells, coal tar, burnt clay, sand-clay, something called sand-gumbo, slag from blast furnaces, and even compressed straw. Towns lucky enough to be close to stone quarries had it made. Gouverneur, New York, paved its roads in 1911 with crushed marble sandwiched around asphalt. The asphalt cost $500 a carload; the marble was only $1.
Around 1900, lumber interests came up with a process of treating wood blocks with preservatives to avoid the problems of earlier wood pavements. Minneapolis, controlled by timber magnates like the Walkers, invested heavily in creosote-treated wood-block pavement from 1902 to 1912. Other cities turned to wood in an effort to alleviate noise problems. Unfortunately, even with the preservative process, wood blocks were too expensive for cities remote from major forest areas. In addition, the sticky chemicals soon seeped out and got all over everything. Within a few years much of the preservative would be gone, and then the pavements buckled, bulged, and rotted just like untreated wood.
In retrospect the eventual popularity of concrete seems inevitable. It was of moderate cost, required little maintenance, was easily cleaned, and held up well. But concrete took quite a while to gain favor. The first American concrete pavements were laid down in Bellefontaine, Ohio, in 1884, and for the next several decades concrete lagged behind brick, asphalt, and wood. One reason was poor workmanship: a few early contractors, unfamiliar with the material, produced improperly built roads that crumbled along the expansion joints. These problems were soon corrected, but they gave concrete a bad reputation that took years to overcome.
Noise was another problem; horses were only slightly quieter on concrete than on stone or brick. There was also considerable local resistance, because pressure to use the products of nearby firms was ever present. In Chicago, where such things as price and quality were minor factors in the awarding of contracts, officials called for treated wood blocks, with the specified preservative being a type of oil produced by only one company in the United States—located in Chicago, of course.
But eventually the soaring popularity of automobiles made concrete the clear favorite. Motorists enjoyed the smooth ride they got on concrete roads and demanded them everywhere; local residents found them to be quieter than brick roads. Concrete proved to be the most cost-effective durable surface when exploding auto traffic placed demands on roads that were inconceivable at the turn of the century. Today’s America would find it hard to function if its interstates were made of anything less tough than asphalt or concrete. But back in 1905 it was not implausible to imagine someday driving from Boston to St. Louis on molasses and wood.