QUALITY ASSURANCE FOR MOBILE RETROREFLECTIVITY UNITS

Transcription

1 State of Florida Department of Transportation QUALITY ASSURANCE FOR MOBILE RETROREFLECTIVITY UNITS FDOT Office State Materials Office Authors Patrick Upshaw Joshua Sevearance Hyung Lee Date of Publication June 2012

2 INTRODUCTION For Mobile Retroreflectivity Unit (MRU) quality assurance, the Florida Department of Transportation (FDOT) has designated a series of laboratory and field tests at the State Materials Office (SMO) located in Gainesville, Florida. The laboratory test consists of a series of experiments that are conducted in a controlled environment (i.e., FDOT s MRU calibration bay). The field tests will be conducted on a series of roadways in Alachua County, Florida, with various pavement markings and pavement types. LABORATORY TESTING The following laboratory tests will be conducted to verify the performance of the MRU, operator, and data collection software: Visual Inspection Alignment and Wander Background Noise Testing Comparison Testing with Handheld Retroreflectometers Visual Inspection Visual inspection is the first step in making sure the MRU is ready for operation. A good practice to ensure the equipment is test ready is to inspect that all brackets, mounts, and bolts are tight and mounted securely around the exterior of the equipment before calibration and routine operation. The retroreflectometer window should be inspected to make sure it is clean and clear of damage and/or debris. If possible, the reflectometer s interior should be checked to ensure that everything is secure. The optics will be inspected to ensure they are clean and clear of damage and/or debris. After inspecting the external and internal components, the MRU should be powered up. The calibration panel will be inspected for damage and wear. The MRU operator will perform the calibration procedure. This process will be inspected to assure accuracy and proper geometry. The retroreflectometer laser power intensity and laser profile will be measured to ensure the readings are within an acceptable range. Extreme arc-like or parabolic shapes should not occur, in order to avoid errors during the data collection process. For a 3.28 feet scan, the longitudinal variation of the laser path should not exceed 3.28 feet. The above visual inspection of the MRU shall be conducted once a month or as deemed necessary. Alignment and Wander Alignment and wander tests are performed to identify proper laser alignment of the MRU and consistency of the retroreflectivity (R L ) value as the laser sweeps across the collection area. Two tests will be performed to determine the extent of the lateral and longitudinal wander while applying the 30 meter geometry. 1

3 Lateral Wander Lateral Wander is a test performed to identify the horizontal laser alignment and the consistency of the R L value as the laser sweeps across the pavement. After the MRU has been calibrated, the calibration panel shall be placed in the center of the software window. With the panel in the center position, a scan shall be initiated and as the reading has stabilized, the R L value will be recorded. The scan will be stopped and the calibration panel shall be repositioned horizontally along the laser path. A new scan will be initiated, and a new R L value will be recorded. This procedure will take place several times moving the calibration panel in increments of 5.0 inches across the 3.28 ft laser path width. At all positions along the horizontal laser path, the R L value shall not differ by more than ±10.0% from the center position. The lateral wander of the MRU shall be tested once every two months or as deemed necessary. Longitudinal Wander Longitudinal Wander is a test conducted to verify the vertical alignment of the laser in order to simulate data collection while traveling along small inclines and declines. The MRU must first be calibrated with a calibration panel placed in the center of the software window using the 30 meter geometry. After a measurement has been taken, 1/2 inch spacers will be placed below the front tires. The panel will be repositioned 3.0 feet behind the 30 meter geometry mark and a new measurement will be taken. Then, the spacers will be placed below the rear tires with the panel repositioned 3.0 feet in front of the 30 meter geometry and another measurement will be taken. In both cases, the R L values shall not vary by more than ±10.0% from the initial reading. The lateral wander of the MRU shall be tested once every two months or as deemed necessary. Background Noise Testing Background Noise Testing is performed to ensure that the noise from the environment and other reflective materials are not influencing the R L values. While measuring a panel as a single stripe type, a second material with lower R L value will be placed to the side of the calibration panel. Neither the R L of the calibration panel nor the background noise value should vary by more than ±5.0%. The background noise testing shall be conducted once a year or as deemed necessary. Comparison Testing with Handheld Retroreflectometers In order to determine if the R L values measured using the MRU are comparable to those from conventional handheld retroreflectometers, a total of six panels (3 white and 3 yellow) with R L values ranging between 100 and 1,000 mcd/m 2 /lux will be tested. After the MRU has been calibrated, the R L of all six panels will be measured with the MRU, one at a time. The R L from the MRU shall be within ±15.0% of the handheld R L values. The background noise will be monitored during this test to see if different panels affect the background noise. The comparison tests shall be conducted once every two months or as deemed necessary. 2

4 FIELD TESTING The following field tests will be conducted to verify the performance of the MRU, operator, and data collection software: Distance Measuring Instrument (DMI) Accuracy Precision Testing Retroreflective Stability and Temperature Test Retroreflective Stability and Speed Test Operational Competency Test Distance Measuring Instrument (DMI) Accuracy The MRU must be equipped with a distance measuring instrument (DMI) to measure the distance traveled by the vehicle. The DMI distance must be within ±3.0 feet when measuring a 1.0 mile section of roadway. The DMI must be calibrated on a monthly basis or as deemed necessary at locations designated by FDOT. Additionally, a recalibration must be performed anytime tires are changed, rotated, or air pressure is adjusted. Precision Testing To achieve repeatable and reproducible measurements between different MRUs, the FDOT SMO designated three field sites specifically used to verify the precision of the MRU. The average pavement marking retroreflectivity for the test sections ranges from 150 to 500 mcd/m 2 /lux. These test sections are located in close proximity to the SMO. The beginning and ending locations of these 1.0 mile sections are clearly marked with white tape. The contractor s MRU will perform a test on each test section while being followed by a FDOT MRU. The pooled results of the contactor s MRU from the three test sections should not differ from FDOT s MRU data by more than ±13.0%. This precision test shall be conducted once every two months or as deemed necessary. Retroreflective Stability and Temperature Test Testing for stability with a change in temperature is recommended prior to using an MRU on actual projects. Temperature may affect the R L values if not properly addressed. This test is designed to demonstrate the long term R L stability. A FDOT designated roadway section will be tested once in the morning and once in the afternoon to verify the effects of ambient temperature on the MRU measurements. A minimum change of 5ºC in ambient temperature must occur between the two tests. Additional MRU calibrations will not be allowed between the two tests. The results from the morning and afternoon tests should not differ by more than ±10.0%. This test shall be conducted once every year or as deemed necessary. 3

5 Retroreflective Stability and Speed Test MRU testing is conducted at highway speeds so it is important to verify the MRU results are not affected by vehicle speed. To verify this, one section of roadway designated by FDOT shall be tested at 35 and 55 mph. The results from the two tests should not differ by more than ±10.0%. This test shall be conducted once every year or as deemed necessary. Operational Competency Test Additional field tests will be conducted to evaluate the following factors: Proper use of event codes such as pavement changes, intersection, turn lanes, etc. Daytime and nighttime testing Driver competency (e.g., vehicle wander) Proper identification of stripes Ability to set R L thresholds for the Raised Pavement Markings (RPM) Proper handling of MRU during acceleration, braking, and stopping For these tests, the MRU will be mounted on the driver side of the vehicle. The tests shall be conducted on roadways with various pavement types and markings selected by FDOT to include the following: Stripe colors - Yellow and white Stripe patterns - Single solid, single skip, double solid, left solid/right skip, left skip/right solid, and edge line Stripe types - Thermoplastic, paint, tape, and audible Various ranges of retroreflectivity Pavement surface - Open and dense graded asphalt surfaces and rigid pavement surfaces Pavement colors Light, medium, and dark (for different levels of background noise) These additional tests shall be conducted once every year or as deemed necessary. QUALITY ASSURANCE Prior to providing MRU services to FDOT, the contractor must demonstrate that their MRU and operator satisfy all of the quality assurance criteria described above. In order to continue providing MRU services, the contractor must conduct the quality assurance tests at the frequency designated for each respective test. Anytime a quality assurance criterion is not met, the contractor must inform FDOT and take remedial action. The contractor must also inform FDOT after remedial action has been implemented and again demonstrate that all quality assurance criteria are satisfied. The quality assurance tests that need to be repeated shall be determined by FDOT after reviewing the problem and the remedial action taken by the contractor. 4