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Pavement-marking technology leaps forward
By Chris Shea
As with all facets of road construction, pavement markings evolve with time. While most people assume state highway departments or county road commissions paint the “lines on the road,” the fact is that private contractors place nearly all pavement markings in the state of Michigan. Most people probably also think these markings are always painted, but in reality, many other materials are used.
Pavement markings are hot thermoplastic, preformed thermoplastic, polyester, epoxy, polyurea, polyurethane, methalmathacralate, or cold plastic tape. Each of these materials require expensive and sophisticated equipment to install, and each material has unique attributes that satisfy particular traffic needs. P.K. Contracting is the only Michigan contractor
that applies all the different materials used
in the state.
P.K. Contracting started business in 1976. At that time, the only materials used to stripe roads in Michigan were solvent-based paints and hot thermoplastic. Solvent-based paints were very cheap but only lasted one year at best.
Hot Thermoplastic Marking
When the government wanted a more durable material, it went with hot thermoplastic. In this process, granular plastic was melted down in large kettles to 430º Fahrenheit and applied to the pavement. Although very dangerous to work with, hot thermoplastic could last up to three years. One drawback to this material was it could only be used on new asphalt pavements. Due to the ambient and surface temperature constraints on applying this material, it was only used between May and September.
Cold Plastic Marking
In the late 1970s and early 1980s, cold plastic tapes were developed to mark pavements. While these materials were significantly more expensive than paint or hot thermoplastic, they were applied to asphalt pavements during the paving process. To further lengthen the marking’s life, the tape was rolled into the pavement by the finish roller. Thus the markings were recessed into the pavement, protecting them from snowplows that could scrape them off.
The very first Michigan project to use cold plastic was on Jefferson Avenue in front of the Renaissance Center in downtown Detroit. Ajax was the paving contractor, and P.K. Contracting did the pavement marking. Although cold plastic markings provided unsurpassed durability compared to paint or hot thermoplastic, they were significantly more expensive and only retained night reflectivity for
two years.
Plural-Component Liquid Marking
Throughout the 1980s and 1990s, material suppliers concentrated on developing materials that would last up to five years and maintain acceptable reflectivity levels. Plural-component liquids were the primary materials developed to satisfy this need. The products used were primarily polyester or epoxy.
While both of these materials lasted up to five years, the equipment needed to apply them was extremely costly and very difficult to operate. In addition, depending on the temperature at the time of application, it could take up to two hours for these materials to dry. The materials were less costly than tape, making them cost effective for use as solid-edge lines, but the difficulty of application and the excessive dry times dictated the need for further technological advances.
Polyurea Marking
In the late 1990s, polyurea was introduced and became the next major advancement in pavement-marking material technology. Although tapes were the best material on the market, their comparatively high cost made them too expensive for use in large quantities such as solid-edge lines.
Polyurea provided the durability of epoxy, while maintaining its color and reflectivity throughout its useful life. In addition, it cured in approximately 10 minutes as opposed to the two hours epoxy could take. Given these characteristics, the Michigan Department of Transportation adopted a standard to use polyurea for solid-edge lines and cold plastic tape for skip lines on newly constructed freeways.
Recessed, Durable Pavement Marking
With a standard in place that took advantage of the best materials available on the market, two factors still needed addressing. While polyurea edge lines and cold plastic skip lines will last five years or more, snowplows can shorten their life by scraping them off the road or by scraping the glass beads off the top, rendering the markings invisible at night. In addition, no pavement marking could be seen at night when it rained.
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| While most people assume state highway departments or county road commissions paint the “lines on the road,” the fact is that private contractors place nearly all pavement markings in the state of Michigan. |
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In early 2001, P.K. Contracting helped develop a system to recess these new durable pavement markings. Large trucks with grooving heads made of stacked diamond saw blades cut grooves in the pavement. The pavement markings are placed in these grooves and thus protected from snowplow damage.
To combat the visibility problem, 3M Company came up with the latest breakthrough in pavement marking. The firm developed ceramic and glass particles that, when applied on top of the polyurea or affixed to the top of the tape in the manufacturing process, provide a pavement marking that maintains its reflectivity at night during a rainstorm. Never before has any pavement marking been visible in dark, wet conditions.
P.K. Contracting is proud to have helped develop a system that provides the motoring public with long-lasting, highly reflective pavement markings day and night, rain or shine. This system is an example of how pavement markings, like asphalt and concrete pavements, continually evolve as contractors and suppliers work to improve their products. To date, P.K. Contracting has applied millions of feet of line using this system on numerous miles of newly constructed freeways.
For more information, contact
Chris Shea at (248) 362-2130 or chris@pkcontracting.com. |
