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Photometry and colorimetry laboratory
for road signaling
Two darkrooms and a so-called "light" room are
among the component equipment of the photometry and colorimetry
laboratory located on the site of the LCPC Paris facility.
The first darkroom is used to perform retroreflection
measurements for both horizontal and vertical signaling
(road markings on the pavement, retroreflective sheetings,
etc.), while the second focuses on luminous vertical signaling
(traffic lights, variable message signs, etc.). The light
room allows studying luminous flux and surface colors
using a set of spectrocolorimeters. The laboratory is
not restricted to evaluating the "visibility"-based
performance of road signaling systems, but also serves
to develop and calibrate measurement devices for visibility
studies and in situ monitoring..
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Traffic light measurement bench |
Bi-directional surface reflection measurement bench |
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· Unit assigned responsibility for equipment operations:
Division for Road Operations, Signaling and Lighting
(ESE)
· Sectors of activity:
- Roads
- Environment and
urban engineering
Contact:
Laboratory for road operation, perception, simulators and simulations (LEPSIS)
An exemplary application:
Development of testing means and methods
Within the scope of the research conducted on vertical
signaling, efforts have primarily been oriented
around measuring the coefficient of retroreflection
on a series of retroreflective sheetings. Investigations
focused on deriving a method for testing measurement
of the coefficient of retroreflection R' of sheetings
based on microprismatic tehnology. This approach
contrasts the indications of currently-applicable
standards that stipulate defining the methods, geometries
and threshold values of R' on the basis of properties
from films produced by glass beads. Over the past
several years, manufacturers have begun marketing
the prismatic-type sheetings which, while displaying
improved performance as regards retroreflection,
yield a spatial distribution of the coefficient
of retroreflection that differs considerably from
the glass beads sheetings; more specifically, this
coefficient may vary heavily depending on the angle
at which the film rotates about itself (see Fig.
1). In the aim of generating a French standard to
cover this type of product, we have tested the behavior
of these films with respect to various geometries
representative of actual use conditions in order
to determine a restricted and sufficient set of
angular combinations that enable controlling the
quality of these products from the standpoint of
meeting user needs (Fig. 2).
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Fig. 1: R' vs. angle of rotation of the film
about itself |
Fig. 2: Calculation of panel luminance for
various films and observation distances |
· Technical characteristics:
- Retroreflector measurement
bench,
- Traffic signal measurement
bench,
- Variable message
signs measurement bench,
- Bi-directional surface
reflection measurement bench,
- Spectroradiometers
for color measurement.
· Operational since: 1982
· Application examples:
- Photometric and
colorimetric testing as part of the NF standardization
procedure for signaling equipment,
- Measurement of the
reference gauge for the purpose of calibrating portable
retroreflectometers
(Ecolux,
Ecodyn, Panolux),
- Photometric characterization
of road surfaces,
- Development and
refinement of testing means and methods within the
framework
of a
signaling equipment standardization protocol.
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