A guide to using the RetroTek-D and ASTM E2832
We frequently get asked about the measurement of ‘wet retro’, so this article aims to answer the questions that typically arise.
It is possible to use the RetroTek-D to measure wet RL on open roads in a controlled environment that prevents water spray from settling on the mobile retroreflectometer unit’s optical surfaces. However, the amount of water, the road marking type and the texture of the marking will all have a big effect on the measured values.
Maintaining safe roadways requires more than just visible lines in broad daylight; it demands high performance during the most hazardous conditions—at nighttime and in wet road conditions. The RetroTek-D is an intelligent mobile retroreflectometer unit designed to measure the retroreflectivity of pavement markings day & night in dry & wet road conditions. The results will be compatible & as accurate as a calibrated hand held measured system.
When it comes to measuring performance of wet road markings,, the industry gold standard is ASTM E2832. Here is how to utilize the RetroTek-D system to ensure your road markings meet these critical safety requirements.
Understanding the Standard: ASTM E2832
ASTM E2832 is the standard test method for measuring the “wet recovered” retroreflectivity of pavement markings. Unlike ASTM E2177 (which measures “wetness” after a period of drainage), E2832 focuses on Continuous Wetting. It simulates a rainfall event to determine how well the beads in the marking reflect light while actively being rained upon.
Why the RetroTek-D?
The RetroTek-D is uniquely suited for this task because it is a dynamic, vehicle front-mounted system. While traditional handheld devices require operators to stand on active highways to take spot measurements, the RetroTek-D captures data at traffic speeds across the full lane width at traffic speeds.
Step-by-Step Operation Guide
- System Calibration
Before any field testing, it is recommended that the operator performs a calibration check on the RetroTek-D to ensure accuracy using the calibrated reference plates provided.
- Setting Up the Simulation
Since ASTM E2832 requires “continuous wetting,” field evaluations typically involve a controlled wetting system i.e. using a method to spray the markings with water.
- The Wetting Apparatus: a vehicle with a spray bar system must be calibrated to deliver a uniform “rainfall” rate as specified by the standard (2 inches of rain per hour). This has to be delivered as a mist at consistent pressure, rather than droplets.
- Equilibration: The markings must be wetted for a specific duration (usually 14 to 30 seconds) before the RetroTek-D records the measurement to ensure the “flooding” effect has stabilized. The area to be tested must be controlled to ensure no vehicles traverse the markings before this period has elapsed and the measurements are taken using the RetroTek-D system.
- Data Acquisition
As the vehicle travels over the wetted section:
- Dual-Line Tracking: The RetroTek-D automatically identifies and tracks both the left and right lines (and even center of lane symbols) simultaneously.
- Geometry: The system maintains the standard 30-meter geometry, ensuring the entrance and observation angles align with ASTM requirements.
- Video Integration: The system records high-definition video synced with the RL data, providing visual proof of the “wet” state of the markings during measurement.
Data Analysis and Reporting
Once the run is complete, the RetroTek-D software processes the raw sensor data into a digestible format:
Feature
Description
RL Value
Expressed in mcd/m2/lx. This is the primary metric for ASTM E2832 compliance.
GPS Tagging
Every data point is geolocated, allowing for GIS mapping of "failed" wet-weather zones.
Pass/Fail Thresholds
The software can be programmed with specific agency thresholds (e.g., >150 mcd/m2/lx for wet recovery).
Key Tips for ASTM E2832 Compliance
- Maintain Constant Speed: Maintain a steady driving pace through the test zone when applying the water.
- Check Water Purity: If using a spray truck, ensure the water is clean. Debris or heavy minerals can coat the marking beads and artificially lower your readings. To deliver accurate wet results , it is recommended that the pavement markings are clean & free from debris.
- Environmental Logging: Record the ambient temperature and humidity, as these variables can influence how water films form on the marking surface.
Summary
Using the RetroTek-D and a vehicle applying water spray to pavement markings to satisfy ASTM E2832, shifts the burden of proof from dangerous manual spot-checks to a safe, automated, and highly repeatable process. By following these steps, road authorities can ensure that their markings remain visible when drivers need them most – in the dark and in the rain.
