DELTA LTL-XL Retroreflectometer 7
SECTION 1
OPERATING INFORMATION
LTL-XL introduction
The LTL-XL retroreflectometer is a portable field instrument intended for measuring the
retroreflection and reflection properties of road markings. LTL-XL measures the R
L
value
(coefficient of retroreflected luminance at night) and the Qd value (day light visibility). R
L
is
a measure of the lightness of the road marking as seen by drivers of motorized vehicles in car
headlight illumination. The road is illuminated at an angle of 1.24The illumination for Qd is
diffuse. The reflected light for both R
L
and Qd is measured at an angle of 2.29, which corre-
sponds, to an observation distance of 30 meters. This is relevant for a motorist’s viewing situ-
ation under normal conditions. Further information on measuring principles and standards can
be found on www.roadsensors.com.
Figure 1. The instrument
The operation of the retroreflectometer is very simple and requires minimal instruction.
The LTL-XL measures the retroreflectivity and calculates R
L
and Qd according to the interna-
tional CEN and ASTM standards. Results are presented in plain text on a large graphic dis-
play. Error messages or warnings are shown in the display in case of any problems during use.
The memory of the instrument provides registration of measurements with corresponding
date, time and other relevant data. The following data is also registered (if enabled):
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