Systematic Degradation of Retroreflective Materials for Testing and Research

Overview

Retroreflective tape helps drivers see large trailers, roadway objects, and safety gear at night. New tape reflects a lot of light back to the driver, but tape that has been exposed to years of dirt, weather, and general wear becomes noticeably dimmer.

The problem is that worn tape never fades in the same way twice. Field samples show large variability driven by:

• Age
• Dirt and abrasion
• Cleaning products
• Environmental exposure
• Manufacturing inconsistencies

The purpose of this study was to find a controlled way to recreate the loss of brightness. Instead of relying on naturally aged tape, researchers reduced the brightness on new tape by printing small dot patterns across the surface. By adjusting how much of the tape is covered, they were able to lower its reflective performance in predictable steps.

The study measured how much the reflected brightness (known as RA) drops based on how much of the tape is covered. Results showed that RA decreases in a straight line, meaning the more you cover, the less it reflects.

How Retroreflective Tape Works

Retroreflective tape is made to send light back toward its source, usually a vehicle’s headlights, so drivers can spot objects from a distance in dark or low-visibility conditions. The reflection helps with early detection of trailers, road signs, and other equipment at night.

There are two main types of retroreflective sheeting:

1) Glass Bead Sheeting

Glass bead sheeting uses tiny glass beads embedded under a clear outer layer. When light enters each bead, part of it is reflected back toward the source. Glass bead tape is common and inexpensive, but it reflects less light and tends to show more variation from one piece to another.

2) Prismatic Sheeting

Prismatic tape uses very small, precisely shaped prisms instead of beads. These prisms return a larger amount of light directly back to the headlights. Because the prisms are uniform in size and shape, prismatic tape is usually brighter and more consistent than glass bead tape.

To measure how bright the tape is, researchers use the coefficient of retroreflection (RA). A higher RA value means the tape looks brighter.

RA can be measured using handheld retroreflectometers. These tools shine a light at a set angle and measure how much of it reflects back. There are two common types:

• Point retroreflectometers, which take a single reading from one direction.
• Annular retroreflectometers, which average readings from all directions around the light source.

These measurements allow researchers to test how visible a surface will appear to a driver under real conditions.

Methodology

To control how much light the tape reflects, the research team printed a pattern of black dots directly onto new retroreflective sheeting. They created ten different versions, each with a specific amount of service area covered.

The team tried several printers to see which ones produced clean, consistent dot patterns:

• Inkjet and Pagewide printers
• Two types of laser printers

Only the laser printers worked properly. The inkjet and Pagewide prints didn’t dry on the tape and smeared with even light contact. The laser printers produced sharp dots that stayed intact.

Before and after printing, each piece of tape was measured with handheld retroreflectometers. These devices shine a light on the tape and record how much of it reflects back.

Three different models were used:

• Two point-based retroreflectometers
• One annular retroreflectometer, which averages readings from all directions

Each reading was taken at the standard entrance and observation angles used in federal testing. Measurements were taken in multiple spots along each strip of tape to get a reliable average.

By comparing the before-and-after readings, the researchers could see exactly how much the brightness (RA) dropped for each dot pattern.

Results

Once all the printed tape samples were measured, the results showed a clear and consistent pattern.

1) Brightness Dropped in a Straight-Line Pattern

Across every test, there was a strong, linear relationship between how much of the tape was covered and how much the brightness dropped.

In simple terms:

• Cover a small amount of the surface → small drop in brightness
• Cover more of the surface → larger drop in brightness
• The drop happens in predictable, even steps

This held true for both types of tape and at both standard observation angles used in testing.

2) The Prismatic Tape Stayed More Consistent

The prismatic sheeting (3M 983) behaved more consistently than the glass bead tape. The glass bead tape showed noticeable variation before anything was printed on it. In fact, two rolls sold as the same product gave different baseline brightness readings.

3) The Choice of Printer Made a Difference

Both laser printers worked, but they didn’t produce the same level of darkness.

• The HP laser printer created darker dots
• The Brother printer produced slightly lighter ones

The difference affected how quickly the brightness dropped as more area was covered. This means the printer model becomes part of the equation when trying to reach a specific brightness level.

Inkjet and Pagewide printers were not usable because the ink did not properly bond to the tape.

3) Color Stayed the Same

Even though black dots were printed on the surface, the red and white appearance of the tape stayed within the required nighttime color ranges. Researchers confirmed this using chromaticity measurements plotted on standard color charts.

4) The Measurement Tools Agreed with Each Other

All three retroreflectometers (both point-based and annular) showed nearly identical patterns as brightness dropped. The trend lines overlapped closely, showing that the method works no matter which device is used.

Field Trial Findings

After the laboratory measurements were complete, the researchers tested the tape under real roadway conditions.

Two different levels of retroreflective tape were placed on a tanker trailer:

• Trailer 1 was fitted with tape that still reflected a moderate amount of light
• Trailer 2 was fitted with heavily degraded tape that reflected very little light

The brightness levels were dramatically different:

• Trailer 1 had an RA of about 239.15 cd/lx/m² (white) and 54.21 cd/lx/m² (red)
• Trailer 2 dropped to around 9.27 cd/lx/m² (white) and 4.41 cd/lx/m² (red)

A vehicle was then driven straight toward the trailer at night using low-beam headlights. Photos were taken at fixed distances using the same camera settings.

At 450 Feet

Only the tape on Trailer 1 was visible. The outline of Trailer 2 could not be seen because the tape was too dim to reflect usable light back to the driver.

At 150 Feet

The degraded tape on Trailer 2 finally began to show up, but it was faint and difficult to see compared to Trailer 1.

These findings reinforce how much retroreflectivity is important for detection distance at night.

Key Takeaways

Retroreflective tape does not stay the same forever. Over time, dirt, weather, and general wear reduce how much light the tape sends back to a driver. Because every piece of tape ages differently, it is difficult to use old, worn tape for consistent testing.

This method gives safety professionals a clear and dependable way to see how visibility changes as retroreflective tape wears down. With reliable test samples, researchers can better measure how far away a driver can spot a trailer, how quickly its outline becomes visible, and how much worn tape reduces nighttime visibility. These small changes in distance and clarity can make a significant impact on how drivers respond on the road.