Choosing Wet-Reflective Technology—An Agency Perspective

Monroe County installs wet reflective pavement markings

By: Terrence J. Rice, Charles A. DiSalvo and Brent Penwarden Monroe County Department of Transportation

Monroe County is always looking for new products and better technologies to effectively utilize what dollars we have and to help improve traffic safety on our roadways. One ongoing concern that we have tried to address has been the reflectivity and service life of our pavement markings. We have found that dark rainy nights result in a challenge for the guidance of motorists along our roadways. Recently, in conjunction with 3M, we installed 3M All Weather Paint (AWP-20) wet reflective pavement marking paint to evaluate whether this product addresses the issue.

In the past, the only way to make pavement markings reflective was to drop glass spheres on the wet paint, and in doing so, the glass spheres would direct light back to its source (the driver’s eye), which is known as retroreflectivity. This method works fine until you have a coating of water (rain) on top of the glass spheres. The water refracts (bends) the light, so that the light striking the glass spheres does not return to its source (the drivers eye), rendering the pavement markings nearly invisible. In order to address this problem in the past, the glass sphere manufacturers have increased the size of the glass spheres, so that hopefully the top of the sphere is above the level of the water, and can still reflect the light back to its source. The drawback to this is that sometimes it rains hard enough so that the glass spheres are still submerged, and, in the snow belt areas, the snow plows tend to shear off the tops of the larger spheres, rendering them useless.

The other old technology was to install "plowable markers"; these are basically "reflective road buttons" that are placed lower than the road surface. These work, but are very expensive and very labor intensive to install.

3M has now come up with a replacement for the glass spheres which they call "dualoptic elements", which are actually retroreflective under water. These "elements" in conjunction with a "high build resin" paint system is called 3M All Weather Paint. Not only does it reflect under water, it’s more durable and lasts longer than conventional waterborne traffic paint.

Last year we witnessed an in-office demonstration of the product, and we decided we would like to actually test the product on our own county roads. In June, 2008, in cooperation with 3M, we purchased introductory quantities of the new product. Since this wet reflective paint requires a double-drop bead system, our crew had to temporarily convert our county paint truck to install the product. Our crew installed double yellow centerline and white edgeline using 3M All Weather Paint (AWP-20) wet reflective paint on two roads (Attridge Rd. and Robertson Rd.) in the Town of Riga.

At this point, we are comparing the wet reflectivity of this product to our current pavement marking paint. If the reflectivity, installation costs and service life are favorable, we will consider using this wet reflective technology on other roads throughout the county.

This article originally appeared in the New York State County Highway Superintendents Association newsletter; reprinted with permission from Monroe County.