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RetroSign GRX Retroreflectometer
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RetroSign GRX Retroreflectometer

  • Description
  • Common Misconception
  • Assessment and Management Rules
  • Literature

RetroSign GRX Retroreflectometer

Assessment Method to maintain Minimum Retroreflectivity - A professional option for measuring all types of retroreflective sheeting on road traffic signs, high visibility clothing, license plates and conspicuity tapes. Alternative Assessment Method: View Cost Effective Sign Dating Stickers

  • The RetroSign instrument: RetroSign GRX is the most advanced retroreflectometer available on the market currently for measuring retroreflection of road traffic signs, high visibility clothing, license plates and conspicuity tapes. RetroSign GRX is built in accordance with existing standards to allow for retroreflection measurement of various colours and all type of retroreflective materials including fluorescence types. RetroSign GRX uses a LED light source and meets the sensor response as stated in ASTM E 1709 for combining the CIE eye response and CIE illuminant 'A'. RetroSign GRX has a rugged design and is built for long-lasting field work even if it can also be used in the laboratory. The software is simple and intuitive and guides the user through the different steps of a measurement program. RetroSign GRX allows the user to create templates with almost unlimited measurement related information (pre-defined or specific entries) of series of measurements with the same basic data. An ID for the user can be entered.
  • Standard compliance: RetroSign GRX complies with the following standards: EN 12899 (road traffic signs), EN 20471 (high visibility clothing), ASTM E 1709 & ASTM E 2540 (road traffic signs), ASTM E 1809 (high visibility clothing) and ECE 104 (conspicuity tapes).
  • Technology: RetroSign GRX is based on point aperture geometry comparable to laboratory readings reflecting real-world driving conditions and allows detection of incorrect application of direction sensitive microprismatic sheeting.
    RetroSign GRX uses advanced sensor technology to allow for measurement of up to seven observation angles in addition to automatic colour recognition. The angles available to the user are: 0.2°; 0.33°, 0.5°; 0.7°, 1.0°, 1.5° and 2.0°. A built-in digital camera makes it possible to take pictures of signs as well as scan barcodes and QR codes for asset management purpose.
    The man-machine user interface is through a large 5” WVGA color touch display clearly visible even in bright sunshine. The instrument automatically detects and compensates for ambient light present which could affect the measurement result.
    The working range of the instrument is 0 – 2.000 cd x lx-¹ x m-².
  • Scalability: GRX scalability - also after purchase - is an extremely powerful feature. Users can upgrade their system in the field as their needs change. The GRX comes with all features but just those paid for are made available.
  • Instrument types: RetroSign GRX is offered in three base models where the figure tells the number of observation angles offered
    · GRX-1 (1 entrance and 1 main observation angle)
    · GRX-3 (1 entrance and 3 observation angles)
    · GRX-7 (1 entrance and 7 observation angles)
    The entrance angle is provided as a front adapter with one of the two standard angles of -4° (ASTM) or +5° (CEN) supplied with the instrument. Further entrance angles of +10°, +15°, +20°, +30°, +40° and +45° are offered for special measurement purposes. In addition, GRX is offered with ECE 104 conspicuity tape multi-angle entrance angle adapter with +/- 5°, 20°, 30°, 40° and 60° angles.
    Using the instrument on continents with different measurement geometries just requires an extra front adapter.
    RetroSign GRX will be available as one model for both CEN and ASTM geometries. The geometry is being controlled by the front mounted entrance angle adapter. The instrument automatically reads which adapter has been attached and records this information.
  • Standard Instrument: RetroSign GRX offers a range of basic features
    · Measurement of 1, 3 or 7 observation angles
    · Calibration reference with values as number or QR code for scanning
    · Automatic color recognition
    · Color contrast calculation (background and legend)
    · Manual pass/fail evaluation
    · Memory of >2 mio measurements, >2,000 measurements with pictures
    · Bosch professional replaceable and rechargeable battery available from the market
    · Data transfer to PC via USB memory stick
    · Data presentation in generally available software like Excel and Google Earth
  • Optional instrument features: RetroSign GRX offers a range of built-in features which add value to the performance of the instrument.
    · GNSS for location identification and mapping
    · Camera for taking photos of signs
    · Camera for scanning of barcodes and QR codes for asset management
    · Wireless communication
    · Instrument rotation and tilt
    · Sign facing direction
    · US MUTCD Library with automatic pass/fail evaluation
    In addition to built-in features the following items are available:
    · Wireless operated extension pole, 1.5 to 2.7 m / 4.9 to 8.9 feet.
    · Entrance angle adapters of -4°, +5° +10°, +15°, +20°, +30°, +40°,+45° and ECE 104 multi-angle adapter.
  • Data presentation: Data can be transferred to another media via WiFi. RetroSign GRX measurements transferred to a PC will be presented as a log file in Excel and displayed on Google Earth. If other output formats are required, DELTA will be able to assist in developing such solutions.

Did You Know?

An assessment method is required to be in place to maintain minimum retroreflectivity of all traffic signs.


Agencies MUST purchase a Reflectometer and use the Retroreflectivity Measurement Method which requires equipment purchases totaling over $10,000.


Agencies DO NOT need to purchase a reflectometer to measure retroreflectivity levels of all their signs. Agencies DO need to implement a program that regularly evaluates and assesses the nighttime performance of their signs. We recommend Sign Dating Stickers as a low cost, budget friendly way to meet assessment method requirements for smaller agencies, rather than purchasing unnecessary equipment. View Cost Effective Sign Dating Stickers

Assessment and Management Rules

The Final Rule issued by the Federal Highway Administration provides five “Assessment or Management Methods” for agencies to implement a retroreflectivity sign management program. Only 1 of the 5 methods must be implemented to diminish an agencies liability.

1. Visual Nighttime Inspection Method: In the visual nighttime inspection method, the inspector assesses the visibility and retroreflectivity of the traffic signs as he or she approaches the signs. Signs need to be replaced if they do not meet the comparison defined in the appropriate procedure.

2. Measured Retroreflectivity Method: In this method, the retroreflectivity of a sign is measured by a Reflectometer and directly compared to the minimum level appropriate to that sign. A sign needs to be replaced if the average retroreflectivity value is less than the appropriate minimum level.

3. Control Sign Method: In this method, a control sample of signs is used to represent the total population of an agency’s signs. The retroreflectivity of the control sign is monitored at appropriate intervals and sign replacement is based on the performance of the control signs.

4. Expected Sign Life Method: In this method, individual signs are replaced before they reach the end of their expected service life. To do this, an agency will need to know the expected service life required for the retroreflective material to degrade to the minimum retroreflective levels, and will need a method of identifying the age of individual signs.

5. Blanket Replacement Method: In this method, an agency replaces all the signs in an area/corridor, or of a given type, at specified intervals. An agency that uses this method does not need to assess the retroreflectivity of individual signs.


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