| MOBILE READINGS
Below: Measuring
the visibility of
road markings is
essential for the
safety of advanced
driver-assisted
systems
Annual Showcase 2020 | Intertraffic World 115
markings by human and vehicle
vision systems. In February 2019,
negotiations between the European
Parliament and the European Council
on a new Road Infrastructure Safety
Directive achieved a milestone with
the agreement that “high-quality
road markings and road signs are
crucial to support drivers and
connected and automated vehicles”.
Once these new minimum and
uniform pavement marking and
sign regulations are in place over the
next few years, road authorities and
DOTs will have a legal and safety
requirement to ensure their roads
are compliant.
Visibility and contrast
Until the advent of driving-assistance
systems in cars, road markings and
the standards that govern them were
geared towards human drivers (Level
0). ADAS functions such as Level 1
features – lane departure warnings,
for example – need to ‘see’ lane
markings to determine if the vehicle
has departed the lane. If the lane
markings can’t be seen properly,
the alert will not be triggered. For a
vision system to image and recognize
lane markings and other road safety
features, there needs to be sufficient
contrast to make the feature visible.
For instance, Toyota’s Lane Trace
Assist technology depends greatly
on the quality of longitudinal road
markings, warning that “depending
on the road conditions... the system
may not work normally” and stating
that the technology is “designed to
read visible lane markers.”
Contrast, the difference in
luminance or colour that makes an
object – or its representation in an
image or display – distinguishable.
The higher the contrast value, the
more distinguishable an object is
and by extension the more visible.
At night, lane markings that have
very good retroreflectivity are
visible because of their high contrast.
Good night-time contrast does not
necessarily translate to the same
during daylight hours. Achieving
good lane marking contrast in a
broad range of daylight conditions
is critical to eventual rollout of
automation Level 3 and beyond.
Vision systems will play a central
part in this rollout, a point of
view put across forcibly by
some vehicle manufacturers.
ADAS systems are sourced
from multiple suppliers. While
they may have similar functionality
with similar performance, all will be
programmed differently and with
different machine vision algorithms.
How are these systems baselined
under different lighting conditions
day or night? How is a measure
of lane marking visibility scored?
Coupled with the standardization
efforts in the US and Europe and the
existing marking standards (EN 1436
and ASTM E1710), validation of ADAS
ability to use today’s roads requires a
mobile, reliable, accurate and traceable
lane marking inspection system.
A third-generation is here
RetroTek is the first in a
new generation of mobile
retroreflectometers that allows
a full road lane to be surveyed in
a single pass, in comparison with
the industry’s previous generation
of single-sided systems.
Using RetroTek, retroreflective
measurements of left and right
road lines, left and right road studs,
median markers and central road
markings are made in a single pass
at normal road speeds by a single
operator. The benefits of measuring
the retroreflective performance of
road marking material are many –
good line visibility saves lives and
significantly, as we move into the
era of self-driving vehicles, ensures
the road network is suitable for
ADAS and autonomous vehicles.
RetroTek deploys technology
that locates and inspects road
markings using methods similar
to those employed by ADAS in
vehicles. Retrotek can help the
pavement markings industry meet
the challenges presented by ADAS
with 100% lane coverage (from
edge to center lines) in one pass
– a 50% saving in travel distance
and time with increased safety
for the operator compared to
traditional side-mounted, single-
line retroreflectometers. n