The reflective material shall have minimum intensity values at each of the angles listed in this section. After the durability test under section 37-02-01-08, the minimum reflective intensity values for the reflective material shall not change more than twenty percent from the values specified in this section.

MINIMUM REFLECTIVE INTENSITY VALUES, R *

Divergence Angle, degrees	Incidence Angle, degrees	Reflective Intensity, R
0.2	0	10
0.2	15	7
0.2	30	5
0.5	0	5
0.5	15	4
0.5	30	2

1. Measurements shall be conducted in accordance with photometric testing procedures for reflex-reflectors as specified in Society of Automotive Engineers Standard, SAE J594, Reflex Reflectors, and using fifty, plus or minus five square inches [322.6, square centimeters] of reflective material. The maximum dimension of the test surface shall not be greater than one and one-half times the minimum dimension. The reflective intensity (R) is computed from the equation.

$$R = \frac{(L_r)(d_2)}{(L_s)(A)}$$

Where:

R = reflective intensity, candlepower per incident foot-candle per square foot.

L_r = illumination incident upon receiver at observation point foot-candles

L_s = illumination incident upon a plane perpendicular to the incident ray at the test specimen position, foot-candles.

d = distance from test specimen to source of illumination one hundred feet (specified in SAE J594).

A = area of test surface, square feet.

General Authority: NDCC 39-21-50

Law Implemented: NDCC 39-21-50