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Pavement Marking Reflectivity

For the collection of pavement marking retro-reflectivity, Fugro can employ the use of the Laserlux® CEN 30 mobile retroreflectometer. The Laserlux is the complete and sophisticated mobile highway retroreflectometer system on the market today. Featuring proven optical head technology, the system objectively measures the retroreflectivity of pavement markings using a scanning laser source. The system ensures that measurements are collected quickly and accurately by incorporating new high-speed data acquisition electronics and software, and precise angular settings of illumination and angle of observation.

The system provides real-time pavement marking reflectivity and can be used either day or night at variable traffic speeds. Designed with CEN 30-meter (98.425 feet) geometry, the system has a scan width of 3.63 feet, giving the user both contrast and retroreflectivity measurements anywhere within the scan width.

Features include Windows 98/ME/NT/2000/XP-based graphical data logging software with a GPS for location data logging, mounting brackets for left- or right-side vehicle measurements, a forward-looking video camera with cab-mounted monitor for driver guidance and cab-mounted video recording camera with data overlay.

Additional features include:

  • Computer-controlled acquisition
  • Utilizes ASTM E1710 30 (98.425 feet)-meter geometry with 6+inches of ground clearance
  • Real-time high speed measurements
  • HeNe LASER source
  • Over 1,150 measurements per mile at 60 MPH
  • GPS gives exact vehicle location with stripe data

Studies using the Laserlux have found several advantages over visual evaluation or handheld systems. A study conducted by Florida Department of Transportation on Mobile Retroflectivity Testing for Pavement Marking Management System reported that the Laserlux can collect more than 1,000 data points per mile in less than a minute with 18-20 scans per second. The scan width of the Laserlux can accommodate some wandering in vehicle movement. Operationally, use of mobile retroflectometers can provide a safer environment for operating staff as they are mounted to the side of a vehicle and collect retroreflectivity as the vehicle drives down the road. An operator inside the vehicle controls the retroreflectometer and monitors the data collection via the connected computer software. Also, the use of mobile units does not induce delay to motorists at the surveying site, and can avoid lane closures, especially when measuring center and lane lines.

The calibration process is based upon the manufacturer's calibration and we place a very high priority on making sure the proper steps and processes are followed to ensure the most accurate and repeatable results. Each unit is cleaned, aligned and given a preventative maintenance overview. Lasers operate at optimum performance when their calibration factors are as close to 1.0 as possible. Therefore, prior to data collection, the lasers and their optical sensors are fine tuned and calibrated to 1.0 on our panels and ceramic blocks. The files collected during this process are documented and stored. When the units return back to the facility they are immediately put back on the bench and compared to the results of the same unit and panels/blocks. This is also documented and the results have to be less than ±5% of the testing. If it is greater than 5%, the client is notified of the discrepancy to see if the data is still acceptable. It has been our experience that most agencies require ±10% for repeatability. If not accepted, we will re-survey the data.

The Laserlux® CEN 30 mobile retroreflectometer provides the following:

  • RL Range (continuous measurement of night visibility): 5 to 4,000 mcd/m2/lux
  • Resolution: 0.06 mcd/m²/lux
  • Sample Rate: 20 scans per second
  • Data points per Scan: 10,000
  • Geometry: ASTM E1710 and EN 1436 30-Meter Geometry

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