California Department of Transportation


Botts' Dots

Yes, the California Department of Transportation is studying the cost and effectiveness of raised pavement markers and their use in varying situations around California.

No, Caltrans is not thinking about getting rid of them any time soon.

Those things that everybody calls "Botts Dots" are actually, in highway parlance, raised pavement markers. Elbert D. Botts was just the guy who, in the 1950s, invented a certain kind of dot and found a way to stick it to the surface of the road. The dots were invented so drivers could see lane stripes in the rain or at night.

Caltrans has used other materials for markers in certain situations (plastic, ceramic, polyester), different kinds of glues (standard and rapid-set epoxies and bituminous adhesives), and different types of stripes (paint, dots, and thermoplastic stripes). And since the department has been using various markers for more than 30 years now, it seems reasonable to step back and take a look at how well they work from two angles: safety and cost.

Safety: Caltrans must consider the safety both of motorists and its workers. While the department does not have extensive data at this time, it appears other kinds of pavement markers may keep motorists about as safe and last about as long in some situations as the raised ones -- plastic stripes, placed on the pavement at high temperature, are one kind.

Caltrans must also protect its workers. Placing or replacing the markers is a one-at-a-time job, and that means that Caltrans or contract workers have to get out there and glue them down. Any time workers are near traffic, they are exposed to drunks, bad drivers and bad vehicles. Anything that shortens workersą time on the roadway means greater safety.

Cost: Caltrans also has to consider whether the first-time plus lifetime cost of the various markers is justified in all situations. Both the durability of the marker and that of the material used to glue it to the pavement are factors. Some materials seem to work better in certain situations -- dry desert conditions as opposed to wet coastal ones, for example -- than others. Some seem to work better where there is more traffic, especially weaving traffic. Raised markers -- dots -- canąt be used where there is snow, because snowplows destroy them.

Caltrans proposes a study, taking these things into account: what is safest for motorists and workers, what works best at given locations, and what costs the least? There is no timetable for the study at present, but it is likely that Caltrans will have the results in six months to a year.

And while Caltrans will consider a full set of alternatives to the dot, it remains likely that they'll be with us for a long time.