Retro reflectance. If properly applied with a drop-on glass bead rate of ten pounds per 100 square feet of either ADOT Standard (Per Subsection 708-2 02 of the Standard Specifications) or AASHTO M247-81, Type 1 glass beads of all the white and yellow thermoplastic materials supplied will have the following minimum coefficient of retro reflected luminance values (retro reflectrometer) 14 to 30 days after application to the roadway surface. Product Color Retro Reflectance White 175 Yellow 100 The units of retro reflectance are millicandelas per square meter per lux. The retro reflectometer will have an 86.5 degrees entrance angle and a 1.5 degrees observation angle. All measurements should be made in the direction of traffic. Compliance with the retro reflectance requirements will be based on a random number of measurements that are taken at representative portions of the applied pavement marking. The City will determine the exact sample locations and number of measurements to be taken. However, the following general criteria will apply: • For transverse lines two measurements are to be taken per lane (one-wheel patch and center of the lane) for which the line crosses (up to a maximum of 20 measurements), • For continuous longitudinal lines a minimum of 20 reading will be taken per line. The spacing of these measurements are to be roughly at the start, midpoint and end point for the line being measured. The minimum distance between any one measurement should be three feet, • For longitudinal lane (or skip) lines a total of two readings per lane line are to be taken with a minimum number of ten lane lines to be sampled. The spacing of the lines to be sampled should be at the start, midpoint and end point in the area to be measured. The minimum distance between the two measurements should be two feet, and • For symbol and legends three measurements should be taken on each individual symbol (arrow) or legend letter. The location of the measurements should be near the top, midpoint and bottom of the symbol or legend • For lines, if 15% of the measurements are below the required minimum then the line segment is to be considered acceptable if no other failure factors (e g discoloration, loss of adhesion, etc.) are involved. For the legends and symbols the average of the three readings should be above the minimum required value for it to be considered acceptable.
