Many drivers in California are mourning their state transportation department's (Caltrans) decision to phase out Botts’ dots on the state's roads. The dots in question are round, raised pavement markers used to mark lanes on highways and arterials in lieu of striping.
Botts’ dots, which are usually comprised of either ceramic or polymer materials, were developed by a Caltrans engineer named Elbert Botts in the 1950s, and California’s state legislature mandated their use on all snowfall-free highways in 1966. (Snowplows damage or dislodge the dots, prohibiting their use in colder climates.) The markers are also used in certain western and southern states, such as Alabama, Florida, Texas, and Nevada, as well as for temporary lane marking in snowier states like Massachusetts and Pennsylvania.
There are over 20 million dots on California highways, and most drivers love them. Crossing a lane marked with Botts’ dots rather than painted stripes results in a rumbling sensation, alerting distracted drivers or awakening sleepy ones. Although a Caltrans study claims that the dots didn’t significantly affect accident rates, the internet abounds with personal anecdotes about sleepy drivers who were awakened by the rumbling on the 405 during rush hour, potentially saving their lives.
Caltrans has some pretty good reasons for phasing them out, however. First, their lifespan is shortening. The dots had about a 10 year lifespan when first introduced in the ‘60s, but traffic has increased drastically since then, so the dots take a severe pummeling that often cracks or destroys them after 6 months of use. In a worst-case scenario, a dot can break in half and fly into traffic. Another major concern is that the dots are non-reflective, so while they conveniently rumble when driven over they’re tough to see at night or when the road is wet. Some dots are installed over a reflective stripe to begin with, but they sometimes interfere with the stripe, impeding its visibility. Finally, Caltrans cites that replacing the dots—which involves walking along the lane and gluing new dots in place—is dangerous for maintenance crews.
Most interestingly, Caltrans is concerned that Botts’ dots might mess with self-driving car technology. Tests have shown that the dots can confuse autonomous vehicle navigation systems, leading to drifting and possible accidents. Personally, I wonder if the tactile feedback from the rumbling dots might benefit a drifting autonomous vehicle in some way.
As far as I know my state doesn’t use Botts’ dots, although we do have rumble strips on road shoulders. But after rush-hour commuting for a number of years I’ve seen many a driver mindlessly drift over multiple lanes. Caltrans could come up with a less burdensome solution that still involves tactile feedback, or maybe California residents will sue the state until they leave the dots in place. Either one seems plausible at the moment.
Image credit: Peter Kaminski / CC BY 2.0
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