This Instructional Memorandum describes the procedure used to measure the retroreflectivity of pavement marking installations to assure conformance to Iowa Department of Transportation Standard Specification requirements. Retro reflective measurements will be taken by Mobile reflectometers measurements as indicated in A below if specified by the contract documents. B and C alternatives are provided should A not be available at the discretion of the engineer.



The testing for final acceptance will be done between seven days and 45 days after installation.


A.    Procedure for testing of Pavement Markings Using a Mobile Reflectometer (Mobile Reflectometer Measurements (MRM))


When specified provide dry retro-reflectivity measurements of longitudinal markings utilizing an independent Contractor using a vehicle-mounted mobile retro-reflectometer utilizing 30-meter CEN geometry in accordance with ASTM E1710, Standard Test Method for Measurement of Retroreflective Pavement Markings Materials with CEN-Prescribed Geometry Using a Portable Reflectometer. The retro-reflectometer shall be calibrated in accordance with the operating manual and calibration guide for each specific machine and vehicle configuration. Measurement shall consist of the average retroreflective readings and standard deviations, as well as contrast ratios, over mile intervals (or over the length of the line if shorter than 0.1 mile) for each type of pavement marking placed.


Provide a measurement report that includes:

1.    State Project Number

2.    Data collection software version

3.    Date and time of data collection

4.    The Highway number with the beginning and ending reference points of data collection rounded to the nearest hundredths of a mile and the beginning and ending coordinates determined by a Global Positioning System receiver with nominal three-meter accuracy, including the direction of travel in terms of increasing or decreasing reference points

5.    Which line is being read (LEL Left Edge line, REL Right Edge line, CL, Centerline, LL Lane Line Skip, 1LL left most LL in multilane, 2LL second to left most LL in multilane (Auxiliary Lane markings are included and will be read separate from edge lines), etc.)

6.    The 0.1-mile interval retroreflective reading averages and standard deviations

7.    The 0.1-mile interval contrast ratio average

8.    An explanation for any intervals that are marked invalid.

9.    A summary of the average retroreflective readings for each individual run file

10.  A summary of the average retroreflective readings in one-mile intervals

11.          A summary of average retroreflective readings based on 0.1-mile intervals.



Provide the measurement report in the form of an electronic database file, or delimited text file, containing all raw data collected. Submit the data to the Prime contractor and into Doc express for the MRM bid Item. Provide a printed summary to the Engineer if requested. Take all readings prior to snow and ice maintenance operations if possible. Excess beads or reflective elements must not be visible before the retro-reflectivity testing is conducted. Collect the data when pavement and markings are dry, clean and no visible moisture is on the road surface. Note in the report any areas where the pavement markings are obscured. Measure centerline markings in both directions. Measure other longitudinal markings in the direction of intended vehicular travel. Notify the Engineer at least 1 Business Day prior to collecting data. Evaluate any replaced or repaired markings per this Specification at no additional cost to the Department.


Procedure for Testing of Pavement Marking Using the Laser Lux Van


1.    Equipment: The mobile retro reflectometer mounted on a van (Laser Lux Van). A handheld Retro Reflectometer with a 30-meter geometry (entrance angle of 88.76 degrees and observation angle of 1.05 degrees.


2.    The measurement of pavement markings will be done in the same direction as the traffic for which the pavement marking is intended. The centerlines, which are meant for either direction of traffic, will be measured in both directions and averaged. Calibration against a certified standard is required prior to taking measurements.


3.    The Laser Lux Van retroreflectivity is averaged for the overall segment measured in a continuous run and averaged for each tenth of a mile segment. The average retroreflectivity of each test section will be calculated from the Laser Lux report.


4.    The average retroreflectivity for the test sections selected will be reported and given to the engineer.


Procedure for Testing of Pavement Markings Using Handheld Retro reflectometer.


1.    Measure each long line placed with at least 5 spot checks (randomly, approximately evenly spaced) per mile.


2.    A 30-meter geometry handheld retro reflectometer will be used (entrance angle of 88.76 degrees and observation angle of 1.05 degrees).


3.    The instrument will be used as per the instructions in its operation manual.


4.    The testing results will be given to the engineer. Contractor shall provide test info to the engineer for any testing completed on Retro-reflective values for any markings they check.


5. Readings will be taken in the same direction as the traffic for which the lines are intended. In case of centerlines the direction in which retroreflective readings are taken will be alternated. The average of the five readings taken will be used to accept or reject that section. Additional readings may be taken to get a more accurate average if desired.



E. Procedure for Legends, Symbols, Pedestrian Crossings, Etc.


For every ten legends, symbols, etc., one will be selected at random for measurement and spot readings taken on the selected legend/symbol. The average of the number of spot readings taken on the selected symbol will be used for determining the retro-reflective value and acceptance of the group of ten symbols, legends, etc.