Ada County Highway District

ACHD's Road Wizard Sunday, December 31, 2017 ACHD's Road Wizard

Street paint/lane lines are "retro" reflective but may not show up well in dark, rainy conditions; top five reader observations of 2017

The Road Wizard Replies

Dear Road Wizard: I called over two years ago about the possible solution of reflective paint on the lane lines. To date nothing has been done. This isn't just an Eagle-area problem; it is the entire Treasure Valley, probably the entire state.


Road Wizard:

The street paint in Ada County is already reflective, as in "retro-reflective." Retro-reflective means that the light is reflected back to the source of the light/headlights, instead of in other directions. This is achieved by adding a layer of glass beads to wet lane paint.

However, the treatment is not always that noticeable. Water on roads can create a thin film that dims the light from the beads.

ACHD has supplemented the street paint/beads with raised retro-reflective pavement markers on major routes. This solves the water problem, but snow plows tend to peel the markers off the road. Replacing them in the spring is a time-consuming, costly effort.

There are other reflective pavement marker varieties that are installed into the road itself so they can survive the passage of plows. ACHD is trying these recessed markers out at a few locations and may expand their use.

But recessed markers are more expensive than the raised version. They also tend to collect sand and dirt, which can diminish their brilliance. They make chip sealing challenging because each marker needs to be protected from being covered up by the new road surface. The other problem is that a chip seal makes the road slightly higher, which changes the angle of the light reflected from the recessed markers enough to make them less effective.

Road agencies are always looking for bright ideas to help with lane-line visibility at night, but the current options all have a dark side.

Dear Road Wizard readers: Thank you for the thoughtful and intelligent letters this year. It has been my honor and pleasure to provide the answers to your questions. Here are the top five observations made by readers from 2017.

In May, "Jane" noted that a road suddenly had two different names just 300 feet apart. Part of Burnett Drive changed to Quercus Avenue as the result of a new subdivision and Burnett's "L" shape. ACHD bent the rules to keep the Burnett name for both sections.

"Paul" wrote in August about "no compression brakes" signs on Ten Mile Road, hoping for one near his home. ACHD realized that the existing signs on Ten Mile near Overland Road were placed before Meridian expanded its limits. Compression brakes are allowed in Meridian, but not elsewhere in the county.

A "road to nowhere" along Capitol Boulevard at Yale Street was reported by "Brice" in October. Although it looks like an old public road, it was built as a private secondary access to offices at that location. The office building was demolished years ago, but a portion of the pavement remained.

Impossible intersections were "found" by "Steve," also in October. A contractor had placed a closure sign for the intersections of "10th and 6th" and "10th and 8th" in downtown Boise. Those intersections do not exist.

"Pam" pointed out a missing five miles on westbound Interstate 84 between Mountain Home and Boise in November. The last mileage sign stated that Boise was suddenly five miles closer than it should be when compared to the previous mileage sign, and the incorrect sign was changed.

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