2 minute read
Colour match
The colour of road markings is important. So how can we make sure that drivers see road markings in the correct colour at nighttime?
Words | Gustavo Felipe Paolillo, Easylux, Brazil
When looking for guidance or essential information on the road, drivers mainly look for markings on the pavement. It is therefore essential that road markings can easily be seen at all times of day. There are minimum retroreflectance values required for nighttime visibility of road markings, but retroreflectance values do not show us how drivers experience the retroreflected colour of the road marking.
The colour of road markings is an important indicator of traffic direction and positioning. Colours must be unambiguous, especially at night, when driving conditions are more challenging.
In the industry, a lot of effort is being made to ensure that white and yellow paintwork can reliably identified in both daytime and nighttime conditions. The ASTM D6628 standard, for example, covers the daytime and nighttime colour of retroreflective pavement marking materials used for traffic control lane markings and symbols on road surfaces. The standard specifies the CIE coordinates (x,y) colour range of marking colours under nighttime conditions at a 30m viewing distance (Figure 1).
The specific colour ranges for white and yellow were established to minimize the possibility that drivers confuse the two colours in different types of light.
Technological validation
The Easylux Mini retroreflectometer has been expertly engineered to measure the nighttime retroreflected colour coordinates (CIE chromaticity) of white and yellow markings.
The way it works is simple. The colour coordinates are stored for each measurement. They are classified according to whether they lie inside or outside the ASTM colour box. This makes it easy to determine whether a road marking has the correct colour at nighttime when retroreflected.
The Mini retroreflectometer has an external light beam. That is, the light shines out of the instrument housing and onto the roadway, ahead of the instrument for measurements of nighttime
CIE
x=0.546, y=0.427 The measured CIE colour coordinates of yellow markings at 30m geometry
visibility (RL), daytime visibility (Qd) and retroreflected colour coordinates. The external beam enables the reading area to be visible, allowing detailed assessments of marking characteristics. It is also ideal for measuring retroreflectivity in wet weather conditions (ASTM E2832 and EN1436).
Assessing the colour of pavement markings is becoming even more important, as road authorities start making more effort to use more sustainable paint pigments, technologies and road marking materials. The Mini retroreflectometer from Easylux has been designed to make it easy to assess the colour of road markings, so there is no need for guesswork. ■
Above: The Easylux Mini retroreflectometer has been expertly engineered to measure nighttime retroreflected colour coordinates Inset: Figure 1: Nighttime chromaticity coordinates for white and yellow colours at CEN 30m geometry (88.76°/1.05°) EN1436 x=0.546 y=0.427
NIGHTTIME RETROREFLECTED COLOR
CIE chromaticity (x,y) as per EN1436, ASTM D6628 and ASTM E2367.
EXTERNAL BEAM
Measurement area is clearly visible for RL, RL-2, RLwet, Qd and CIE chromaticity (x,y).
