Annual Showcase 2020 | Intertraffic World 167
Above: What
retroreflective
markings look
like up close
Below: Markings
being applied to
a road surface
night. The RI of both the optic
and the air surrounding the optic
determine how much the light bends,
and whether enough light returns to
the driver or camera to be highly
visible in nighttime conditions.
Pavement markings vs rain
Over the years, road planners, traffic
safety experts and departments
of transportation (DOTs) have
become increasingly aware that a
disproportionate number of crashes
occur in rainy, night-time conditions.
“We saw an upswing in the
number of fatalities across the State
of Georgia,” said Andrew Heath,
Georgia DOT State Traffic Engineer.
“When we looked at the data, we saw
that a tremendous number of those
fatalities were happening in wet
conditions and in night conditions
across the state, so we knew that
we needed to get products out there
that directly influenced that trend
to ultimately try to bring those
numbers down.”
One of the first factors they
pinpointed was the difficulty of
seeing pavement markings in rainy
night-time conditions. This is due
to the RI of the pavement marking
optics, of air and of water. Water
has a higher RI than air. When the
pavement marking becomes wet or
when water covers the optics in the
pavement marking, light enters and
exits the glass optics at different
angles. As a result, the light from
the headlamp is not reflected back
to the vehicle but, rather, is spread
out in a much broader, weaker
cone, rendering the pavement
marking invisible.
Technology to the rescue
In the last decade, manufacturers,
engineers, researchers and safety
experts have collaborated to develop
pavement markings that deliver
exceptional visibility in all conditions
– day or night, rain or shine. The
result of this collaboration is wet
retroreflective pavement markings,
or pavement markings that employ
retroreflective optics with a higher
2.4 RI. The higher RI ensures that,
when a pavement marking is wet,
light is still returned to the source.
As a result, wet reflective
pavement markings ensure that
light from headlights is reflected
back to the vehicle, even in the rain,
making the wet reflective pavement
markings visible in both wet and
dry conditions.
Retroreflectivity on demand
Pavement markings play an
important role in improving road
safety, reducing crashes and saving
lives by helping drivers stay in
their lanes. However, for pavement
markings to be effective in this
role, they need to be visible in all
conditions. As we’ve seen, nighttime
rainy conditions make it more
difficult for drivers to see standard
pavement markings, thereby
increasing the risk of crashes,
injuries and fatalities.
Wet retroreflective pavement
markings are specifically designed to
overcome this challenge and deliver
exceptional visibility in all conditions
by using high RI retroreflective
optics to ensure visibility in wet
conditions, in combination with
lower IR optics that effectively
return light in dry conditions.
Studies show that the safety
benefits of this approach are
significant. In 2015, the US Federal
Highway Administration conducted
a rigorous before-and-after
evaluation of wet retroreflective
markings in Minnesota, North
Carolina and Wisconsin.
Over the course of this study,
the researchers determined that wet
retroreflective pavement markings
reduce crashes with injuries by
40% on multi-lane roads and 12%
on expressways.
Then, a 2019 study by the Texas
Transportation Institute found
that wet retroreflective pavement
markings reduced rainy night-time
crashes by 30% and rainy nighttime
fatalities by 50% in TxDOT’s
Atlanta District.
As traffic experts, road planners
and infrastructure developers, we’re
all committed to building safer roads.
By implementing wet retroreflective
pavement markings that deliver
exceptional visibility and clear,
consistent lane guidance in all
conditions – day or night, rain
or shine – we can help reduce
crashes, save lives and bring
families home safely. ■
40% The reduction in the number
of crashes with injuries, on
multi-lane roads with
wet retroreflective
pavement markings
| LANE MARKINGS