What happens to lane
markings when it rains?
Improving road safety with wet
retroreflective pavement markings
Words | Andrew Goodrich, 3M, United States
Above: Road
markings are
difficult to see in
wet, night-time
conditions, but
retroreflective
markings are proven
to increase visibility
and reduce fatalities
Around the world we lose
1.25 million lives to traffic
crashes every year. Nearly
half of those collisions –
49% – happen at night, even though
we only do 25% of our driving after
dark. Rain increases the risk of
crashes by as much as 57%.
Driving in the rain at night
is challenging. Motorists have to
deal with decreased visibility, slick
roads and distracting headlights
from oncoming traffic. But the
greatest challenge may be the fact
that some lane markings become
virtually impossible to see in wet,
dark conditions, which can
sometimes make it extremely
difficult for drivers to stay on
the road, let alone in their lane.
There are solutions to the
problem of pavement marking
visibility in the rain but, before
we consider them, it helps to
understand why many types of
pavement markings are harder
to see at night and in the rain.
How pavement markings work
Since motor vehicles first started
growing in popularity, road planners
166 Intertraffic World | Annual Showcase 2020
have made it a priority to provide
consistent, clear and cost-effective
lane guidance in all conditions, good
or bad. Over the years, solutions
evolved from simple painted white
lines in the early 1900s to the variety
of retroreflective liquid pavement
markings, pavement marking tapes
and raised pavement markers (RPMs)
we see on the roads today.
Retroreflective liquid pavement
markings were first developed to
increase lane visibility at night. The
most common liquid pavement
markings consist of spherical
glass beads (optics), typically with
a refractive index (RI) of 1.5, dropped
onto the lane marking and attached
using a binder. This binder contains a
pigment (usually yellow or white) to
provide color and serve as a reflector.
As light from a vehicle’s headlamps
hits each optic, the light bends,
reflects off the pigment on the
backside of the optic, and bends
again as it passes out of the optic to
return a cone of light to the driver –
or camera on automated vehicle
machine vision systems – and makes
the pavement marking visible at
LANE MARKINGS |