Safety Evaluation of Wet-Reflective Pavement Markings

Appendix. Additional Installation Details from States

The following appendix presents additional details provided by the three participating States regarding the installation of the subject strategies in that State. State transportation departments were asked to provide responses to the following questions:

1. Can you provide any installation guidelines for the markings? For example, width, spacing, minimum levels of initial retroreflectivity?
   
   
2. Are there any criteria for deciding which roads receive the wet-reflective markings? For example, a certain level of AADT, a critical crash rate etc.?
   
   
3. Were any other safety countermeasures installed in conjunction with the wet-reflective markings at the treatment sites evaluated by this study?
   
   
4. Please describe any notable challenges related to the markings installation and how you overcame them.
   
   
5. Please describe any notable challenges related to the markings maintenance and how you overcame them.
   
   
6. What lessons learned or recommendations would you share with another State interested in the widespread application of wet-reflective markings?

Responses From Minnesota

1. Widths and spacing follow normal striping practices. Some wet reflective markings are recessed. Minimum levels of retroreflectivity follow standard specifications: Latex: White-275, Yellow-180, Epoxy: White-300, Yellow-200, Tape: White-600, Yellow-500.
   
   
2. Districts decide where they would like to install wet reflective markings based on their needs. In general, it will be roadways with an ADT > 1,500.
   
   
3. These were stand-alone striping projects.
   
   
4. One challenge we have noticed when looking at wet reflective installations after the fact is that the distribution of the larger elements is sometimes sporadic. Some areas will have good coverage and some will have light coverage. This may be remedied by making sure striping companies have double drop systems and their application ratio of bead/elements is following the manufacturer's specifications. Another possible challenge is groove depth. Substandard grooving contributes to accelerated wear on the wet reflective elements.
   
   
5. One maintenance challenge is the shorter life span of the wet reflectivity of these markings. From our experience, wet reflectivity lasts around 2 years. Beyond that, the dry reflectivity is still well beyond minimums. It would be great to have a way to refresh wet retroreflectivity.
   
   
6. We would recommend recessing all wet reflective markings. Inspect installations to make sure element/bead coverage is good.

Responses From North Carolina

1. The only “wet-reflective” marking we have approved is cold-applied plastic. Although it is approved, we do not have a detailed specification for wet-reflective markings. The minimum initial retroreflectivity for this cold applied plastic is 250 mcd/lux/m² for white and yellow. The only reason this is approved is due to the manufacturer only makes this type of tape.
   
   
2. At this time, we don’t have any safety data showing a positive impact for wet-reflective marking. There are no specific criteria for installation. If a need is seen to install wet reflective markings due to an unusual circumstance it may be done. There is no AADT at which we do or don’t install these types of markings.
   
   
3. No other safety countermeasures were installed in conjunction with the wet-reflective markings.
   
   
4. Our biggest challenge to marking installation is improper installation. This is not a regular occurrence, but it does happen. This is usually do to improper surface preparation and/or cleaning or poor workmanship (not applying the material correctly, applying too much or too little material, etc.). We overcome this by working with the installer to find out what the installation issue is and how it can be corrected. Additionally, we have an annual pavement marking training for DOT and contractors.
   
   
5. We now know enough about the types of markings we use, that if it’s installed correctly we can predetermine its life-cycle (through studies and historical performance). One of our biggest challenges to marking maintenance is snowplowing. We overcome this by installing lower profile markings (polyurea) in locations that see moderate to heavy snowplowing.
   
   
6. Show us a benefit.

Responses From Wisconsin

1. Standard pavement markings specifications are used for wet-reflective products. The minimum required retroreflectivity is 250 mcd. based on the ASTM E2177 test.
   
   
2. On newly paved or resurfaced roads wet-reflective tape is applied for the lane lines and gore areas on freeways, expressways or multilane divided roads. On existing pavements 3 years old or greater wet-reflective tape is used to supplement sprayed epoxy markings at the end of lane lines on concrete and faded asphalt freeways/expressways.
   
   
3. Some locations had either shoulder widening and/or shoulder rumble strips installed. (NOTE: This amounted to approximately 113 mi of the 600 mi used, mostly on freeways).
   
   
4. Initially, all of the wet reflective tape was inlaid into the asphalt surface which shortened the longevity of the tape. For several years, all tape is now grooved in a 120 mils slot no matter the surface of asphalt or concrete. The initial 10 day wait requirement for grooving in asphalt was causing completion delay so with the agreement of manufacturer and those at WisDOT in the pavement area, it was lowered to 5 days.
   
   
5. Inlaid tape was being removed by snowplow activity, thereby increasing the frequency of replacement/maintenance of the tape. Placing the tape in a groove decreased this problem.
   
   
6. Place all wet reflective tape in a grooved slot.

Acknowledgements

This report was prepared for FHWA, Office Safety Research and Development under Contract DTFH61-13-D-00001. The FHWA Contract Officer’s Technical Manager for this project was Ms. Roya Amjadi.

The project team gratefully acknowledges the participation and assistance of the following organizations for this study:

Minnesota Department of Transportation.
North Carolina Department of Transportation.
Wisconsin Department of Transportation.