Delta PG-40 Specifications download pdf (Page 14)

14 LTL-X Retrometer DELTA

SECTION 2

GENERAL INFORMATION

The measurement

The LTL-X retroreflectometer measures the R

(coefficient of retroreflected luminance) pa-

rameter. The R

parameter represents the brightness of road markings seen by drivers of mo-

tor vehicles by headlight illumination.

In the LTL-X the illumination angle is 1.24 degrees and the observation angle is 2.29 degrees.

According to both ASTM and CEN standards this angle simulates a driver’s viewing distance

of 30 meters. The instrument’s illumination field is approximately 200 mm x 45 mm and the

observation field is approximately 610 mm x 60 mm. The dimensions are given for plane sur-

faces. For real non-planar road markings the fields are elongated. The measurement field

is identical with the illumination field.

The figure below shows the placement of the fields for normal and continuous wetting opera-

tions. For continuous wetting measurements the instrument is raised 7 mm by mounting the

wet night rails (See pg 48).

In this operation the illumination/measurement field is placed just in front of the horizontal

base cover allowing the continuous wetting.

Figure: 2 – Measurement field

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Delta PG-40 Specifications Page 14