Retroreflectivity Maintenance
Calibration Signs Procedure
Calibration signs are viewed prior to conducting the nighttime inspection. The calibration signs have retroreflectivity levels at or above the minimum levels. These signs are set up where the inspectors can view the calibration signs in a manner similar to how they will conduct the nighttime inspection. The inspector uses the visual appearance of the calibration sign to establish the evaluation threshold for that night’s inspection activities. The following factors provide additional information on the use of this procedure:
- Calibration signs are needed for each color of sign for which there are minimum levels.
- The calibration signs are viewed at typical viewing distances and from the same vehicle that will be used for conducting the inspections.
- The calibration signs need to be properly stored between inspections so that the retroreflectivity of the calibration signs does not deteriorate over time. Calibration sign retroreflectivity is checked at periodic intervals to ensure that the calibration panels have the appropriate retroreflectivity levels.
- Field signs need to be replaced if the inspector judges a sign to be less bright than the appropriate calibration sign.
Calibration Signs Procedure Checklist
- Be well rested
- Select inspection vehicle and have headlamps aimed
- Select inspection routes (both directions)
- Prepare inspection forms (example shown later)
- Have sign list if available (for each inspection route, a list of signs you expect to see, in order of the direction of travel)
- Clip board, pen lights, dash cam, tape recorder, laptop
- Cannot start in earnest until complete darkness
- View calibration signs before starting your inspection routes