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On the Button : The Quest to Perfect Botts' Dots Continues


In the era of "smart highways," in which computerized cars and roadbed sensors can help a driver avoid accidents, detect congestion ahead and map out the fastest route home, they might seem like little more than anachronistic bumps in the road.

But when it comes to keeping cars on the straight and narrow, Botts' Dots have accomplished far more for less money than any number of electronic gizmos under development.

Named for Elbert D. Botts, a senior state chemical testing engineer who died in 1962, the raised pavement markers that jostle sleepy drivers awake and help everyone find their lanes in the rain have preempted countless accidents and given the Golden State another "first" that is sweeping the world.

Not that anyone would guess this from the festivities marking their 25th anniversary of use. There aren't any planned.

But events leading up to the day a quarter-century ago when legislators mandated the little lumps for all snow-free highways illustrate not only California's attention to freeways but also its willingness to subsidize car travel in ways not apparent to the drivers who benefit.

Considering that 17,067,400 dots had been plopped on the pavement by 1989, the date of the most recent census, there are more Botts' Dots in California than there are autos to run over them, and about 4,100 more are pasted in place each day. Even as the utilitarian saucers make an impression on millions of drivers, the scientific quest for a perfect dot proceeds unabated.

"Research continues" at Caltrans, said Earl Shirley, chief of the new technology division of the state transportation department materials and research laboratory in Sacramento, "and, in the private sector, people always come up with new ideas that they want us to check out."

New designs are now torture-tested on California 99 south of Sacramento, where lots of trucks make lots of lane changes. Any design that survives that extraordinary pounding is eligible for a place on the state's highways--and on the lane-marker history board, a kind of Dot Hall of Fame, that takes up a wall in the Caltrans lab.

"We have every kind we've ever used up there," Shirley said. "There are little ones and big ones; cement ones and metal ones. All types."

Right now, said Russ Snyder of the Caltrans district in Los Angeles, where 3.2 million dots reside, "there are all kinds of these little jobbers" approved for California's freeways. Actually, there are five approved models--plain, round "button dots" in white or yellow, and reflective square "wedges" in white, yellow, and red and white.

Reflectors are mostly plastic. Buttons, the most common variety, are made of clay, plastic or polyester, and can hang onto a highway for as long as six years. Pounding truck traffic in Los Angeles has been known to dislodge some in as little as six months.

"It depends on a lot of things," said Caltrans spokeswoman Mariana Mejia, "including the amount of traffic, the amount of truck traffic and the amount of lane changes."

In some spots, Mejia noted, Botts' Dots have outlasted the road underneath them. She said that in deserts, especially, "the dots are often harder and more durable than the pavement."

Mejia said the plain dots cost about 40 cents each, while the fancy reflectorized ones run about a buck apiece. Shirley added that despite popular and persistent rumors to the contrary, they are not patented. The only people to make money off them are manufacturers--more than a dozen in the United States, Mexico and Taiwan.

Each vies to satisfy California's appetite for about 1.5 million dots a year, Mejia said. With so many to choose from, Caltrans samples each lot of 25,000--testing for color, reflectivity, bondability and, most important, the ability to resist cracking.

California is particularly finicky because it is where Botts' Dots were born.

Caltrans, when it was still the Division of Highways, toyed with the idea of raised markers as early as 1936. But the notion did not gain any urgency until 1953, when traffic volumes and speeds began to climb on the new freeways.

Development of durable epoxy resins also speeded development of markers by letting engineers attach bumps to roads without using spikes, a potentially tire-flattening alternative should the bump break and expose the metal.

At first, engineers toyed with the idea of depositing epoxy lumps on highways, but that was rejected as too expensive and difficult. Instead, they opted to experiment with using the new glue to bond markers to roads.

But markers made of what? Cast epoxy resin was an obvious candidate, but several other materials also had supporters--from relatively cheap Portland cement to more exotic polyester filled with reflective glass beads. Some scientists advocated a simple button shape, while others lobbied for a streamlined wedge.

In the spring of 1955, a team of state highway engineers left their laboratory and ventured onto a new freeway in western Sacramento to test their theories.

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