Snowplows, de-icing chemicals, winter weather and tire wear are formidable foes for the stripes on Idaho’s highways. In a battle of longevity, winter usually wins; stripes usually lose.
Beginning this spring, ITD will employ a new weapon in its campaign to make pavement lines more visible and last longer. A recently approved contract calls for 1.6 million linear feet of durable pavement markings – highway stripes designed to last up to four years, or longer.
“The intent is to increase safety by extending the functionality of pavement markings,” explains Carl Main, maintenance services engineer in the Office of Highway Operations and Safety. “Stripes tend to wear off through the winter. We try to refresh them at least once a year, sometimes more often.”
The water-based paint that ITD uses for most of its highway markings serves the system very well, except in areas with high traffic volume and where abrasives like sand and gravel and regular scrapes from snowplows diminish their visibility. In those vulnerable areas, center and edge stripes may need to be repainted three or four times a year.
New durable pavement markings – actually a four-inch wide thermoplastic tape – should make repeated annual applications unnecessary on targeted highways.
The new contract for durable markings, awarded to 3M Company in February, does not specify the type of material to be used, but places a condition on its longevity. The contractor chose its own product, a thermo-plastic tape, explains Regional Engineer Gary Moles.
Crews grind grooves in the pavement to a depth of about 1/8 inch; grooves then are cleaned and primed in preparation for the strips of tape. The recessed design, Moles explains, reduces wear from snowplows and the tires of vehicles that stray across center lines.
Application of the durable pavement marking should begin between mid-April and mid-May and must be completed within 70 working days, he said. The project includes lane lines only (center and edge), not arrows, turn lanes, stop lines or railroad markings. Work is planned in all of Idaho’s six districts, but ironically, not within Moles’ region – the northern portion of District 3.
After installation of the markings, an independent contractor will test the “retro-reflectivity” qualities as a benchmark every year for the next four years.
“Four years is a good expectation for the product,” says Ron Wright a chemist supervisor in the Materials Section at Headquarters. “We have used 3M tape for years, but this is a new, longer lasting generation.”
He said the durable pavement-marking project might be the first of its kind in Idaho – covering the entire state under one contract. Each district identified areas where stripes are most vulnerable to wear and are best suited to longer-lasting stripes.
Motorists might not notice a difference in reflectivity between the new durable markings and new paint applications, Main explains. The most noticeable difference will be next winter and spring when conventional paint has faded and the durable markers remain much more visible.
Main said ITD will continue to use the more conventional painted stripes in other areas of the state. “I guarantee, we will continue to paint Idaho,” he said.