Vehicle Traffic Control Signal Heads: - Institute of Transportation ...

Almost all manufacturers can provide the
purchasing agency with initial module light
output values. This may be also available from,
or verified by, an independent photometric
laboratory. During the lens cleaning process,
sample readings may be taken from some
modules (or modules suspected of defects) either
by removing it and sending it to a laboratory, or
in situ with a portable calibrated light meter.
This process is particularly important as the
warranty period offered by the manufacturer
comes to an end. If such data are recorded for
the same modules over time (with proper
adjustment for temperature or other factors), an
agency can monitor the light output loss of its
modules over time and take action (for example,
establish a group replacement or similar relamping
approach) to minimize the potential for
inadequate signals.
Note of Caution: A properly calibrated portable
light meter may be used to measure the change
in luminous intensity as a percentage of the
initial intensity. However, portable light meters
will not necessarily provide an accurate
measure of the actual luminous intensity of LED
traffic signal modules.
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