Here’s the meaning behind Caltrans’ road markers
California’s iconic Botts Dot, the bump that warns you’re drifting out of your lane, has reached the end of its road.
After more than a half century of service, the safety device created by Elbert Botts in a Sacramento lab and once described by a state official as a loyal old dog, is expected to be relieved of duty sometime this year. The classic white ceramic dot, a notable innovation in its day, appears to be a bad fit as a lane marker in the emerging new world of driverless cars that rely on cameras, radar and computers to “read” and understand lane lines.
Although automated vehicles can be taught to “see” a variety of lane markings, including dots, federal officials and the vehicle industry say they want more uniformity nationally on lane lines. Given that few states outside of California still employ the original cookie-shaped ceramic Botts Dot, the writing is on the wall.
“My sense is Botts Dots are on their way to extinction,” says Paul Carlson of Texas A&M University, who is leading a national effort to explore what types of roadway devices, including lane markings, are best for the self-driving car era.
Carlson’s project is sponsored by the American Association of State Highway and Transportation Officials, of which Caltrans is a member, and by a group of engineers and commercial vehicle researchers, SAE International.
“All (highway departments) are asking, ‘What do we need to do with our infrastructure to accommodate those technologies?’ ” Carlson said.
That may mean more use of thermoplastic lane lines, a material used by Caltrans and other states that looks at a glance like paint, but is thick like cake icing, and is reflective and more durable than paint. (In snow areas, though, Caltrans and other states use regular paint and reflective markers embedded in divots below the road surface where they won’t get scraped away by snowplows.)
Duper Tong, chief of Caltrans’ Ofﬁce of Trafﬁc Engineering, said the state likely will formally decide this year to begin removing the Botts Dots, possibly more than 20 million of them, from state highways and freeways. The dots would be removed over time when crews do road resurfacing projects, he said.
Automated cars aren’t the only reason for the end of the dot era, Tong said. The dots, which are typically glued to the pavement in rows of four, crumble and break loose too frequently under heavier truck traffic, he said. Caltrans officials say it is risky for maintenance crews to replace them amid speeding freeway traffic.
Tong cited the state’s aging population as another factor. The leading edge of the baby boom generation is now turning 70. Tong said reflective thermoplastic lines and newer reflective plastic markers are easier for older eyes to see. Although white and ceramic, Botts Dots are not considered reflective.
The dots already have largely disappeared in some areas of the state. Caltrans has largely done away with Botts Dots on Sacramento Valley highways in favor of brighter striping materials.
Sacramento city and county also phased out Botts Dots a few years ago on surface streets in favor of plastic “paint” and reflective markers, although you can still occasionally see a few leftover Botts Dots stubbornly sticking to the pavement here and there.
The dots have some sentimental value in Sacramento. They were invented in 1953 in a Caltrans test lab here headed by chemical engineer Elbert Botts. Caltrans was looking for a replacement for painted lines, which were beginning to wear out too quickly on multilane freeways, where vehicles moved from lane to lane.
Botts and his group initially tried nailing the dots into the pavement, but the nails came loose. The state came up with an epoxy to glue the dots down.
Rumors that Botts himself received a penny royalty for every dot the state used are not true, according to the urban legend-busting Snopes website. In fact, Botts is said to have died in 1962, before the state began widespread use of his namesake domed dots.
The dots quickly became useful as a safety tool in more ways than Caltrans envisioned, at least according to some drivers.
Caltrans engineers say they intended the dot to be merely a visual lane delineator. But drivers discovered the rows of dots caused a distinctive ka-thump sound when tires passed over them, offering an audible warning to drivers that their car was drifting out of its lane. Some drivers said they could even feel the vibration.
Norm La Joie of Reedley says Botts Dots once saved his life.
“I fell asleep and the vibration from the dots woke me when I was drifting off the road heading for cement pillars supporting an overpass,” La Joie said. “Nobody knows how many people were lucky like I was. When your eyes close, reflective tape won’t help.”
Tong and other Caltrans officials say they believe the thumping sound is at best a minimal safety enhancement. They point to a Caltrans study in the 1990s on several highways, including the Capital City Freeway in Sacramento, that suggested crash numbers are the same with dots as they are with newer reflective lane lines and markers.
The dot’s imminent disappearance may feel like the passing of a friend among some drivers who grew up with the bumps. Some drivers did complain in the 1990s when Caltrans introduced a new generation of angular, reflective, plastic markers. A Caltrans spokesman at the time, Jim Drago, calmed concerns, assuring drivers the dot was sticking around and likening it in an interview with the Los Angeles Times to a “loyal, good old dog.”
Tong, Caltrans’ chief of trafﬁc engineering, takes a more objective approach to the dots.
“I don’t have any emotional attachment,” Tong said recently during an interview with The Sacramento Bee at Caltrans headquarters across the street from the state Capitol in Sacramento. “I haven’t worked here that long.”
He brought with him a handful of newer lane markers and plastic lane line samples, spreading them out on a conference table.
The state not only intends to increase usage of thermoplastic striping, he said, it likely also will increase lane line widths to 6 inches from the current 4 inches to make them easier to see.
Tong said the state also plans to use more of what it calls “Oreo” or “contrast striping,” a white line flanked by black stripes. That striping, now in use on some Sacramento-area freeways, provides better visibility on light concrete road surfaces.
“We always look at better ways to maintain the highway,” Tong said. “We always look for innovation ideas, new things.”