| ROAD SIGNS
OCR Developments in optical
character recognition
technology will improve
shape and legend
recognition in the
coming years
Annual Showcase 2020 | Intertraffic World 171
with high-pixel resolution to gather
data. These systems continuously
monitor vehicles moving in the same
direction, oncoming traffic and
vehicles stopped on the roadside
that are either parked, merging or
waiting to merge. Some cameras are
coupled with radar systems that ping
the surroundings with a radio wave
looking for the echo when waves
bounce off surrounding objects.
In this mode, the camera system
functions as the first or second
line of warning for the vehicle’s
computer systems, with the primary
responsibility to detect and avoid a
physical interaction with the object.
Traffic signs
Camera-based TSR technology
has improved over the past decade.
The most significant TSR work has
taken place in Europe with speed
limit signs. A number of technology
companies have developed sign
detection and classification
software and deployed it in limited
geographies on select models offered
by car manufacturers including
BMW, Mercedes, Mazda and Honda.
Today’s camera systems have not
advanced to the level of a human
driver – who can read and interpret
the variety of messages in regulatory,
warning and informational signs
– nor can cameras identify and
interpret traffic signs on par with
their human counterparts in the
blink of an eye. Light conditions,
signs at severe angles of approach
or that have been hit and knocked
askew, signs covered by dirt or
dew, or signs obscured by large
vehicles in the camera’s field of
vision all pose challenges for
visual-dependent systems.
The variation in traffic signs
around the world also contributes to
the difficulty of consistent, accurate
detection and recognition. Each
European sign class employs greater
use of shape, border widths and
colors not only distinct from each
class, but from most things seen
in a roadway environment.
The US sign elements are not as
distinctive and visually strong as
their European counterparts.
Warning signs may use
yellow, orange,
fluorescent yellow
or yellow-green.
Only stop signs
and railroad
crossing signs
have messages
specific to their
shape. Many
US signs convey
their message
by text alone,
whereas European
signs feature
pictograms and other
icons that aid recognition.
Advancing technology
Improved optical character
recognition (OCR) technology is
expected to take shape and legend
recognition to the next level in the
future. However, even with enhanced
technology, systems will have to
contend with non-uniformity of size,
font style, and text location prevalent
on today’s traffic signs.
The camera vision industry
acknowledges that traffic sign
recognition can be improved in many
ways. These include increasing sign
size to assure signs exceed minimum
pixel size filtering and are detected
at a greater distance to allow longer
processing and reaction time by the
TSR system; using the symbol sign
equivalent of the text version of
warning signs; and standardizing
font type, size, message and sign
placement. It is also crucial to adopt
sign maintenance practices to keep
signs clean and unobstructed by
vegetation or other roadway
infrastructure, offering a clean
line of sight for cameras.
Advancing technology
Similar recommendations for
improving signing already exist. In
June 2014, the US Federal Highway
Administration described multiple
improvements in their ‘Handbook for
Designing Roadways for the Aging
Population’. Larger signs and letters,
brighter and more uniform
signs all extend detection
distances, improving
safety by giving
drivers longer
time to process
information and
react. These
improvements
– and those
advocated by
the camera
industry – will
benefit TSR
systems, non-
ADAS-equipped
vehicles, and human
non-motorized roadway
users like cyclists and pedestrians.
It will be many years – perhaps
decades – before transportation
systems experience a complete fleet
change to self-driving technology. In
the meantime, traffic signs need to
accommodate the needs of all road
users, including those without the
technology, through all stages of
autonomous vehicle deployment.
Agencies have a clear path on signing
improvements to prepare for
tomorrow’s technology.
Start today by reviewing the local
agency’s standards to ensure they are
consistent in fonts and letter height.
Make greater use of symbols, increase
sign size, adopt maintenance practices
to review signs in the field and
ensuring they are properly placed,
and allow unobstructed viewing. This
is a practical solution incorporating
today’s materials, processes and
proven safety measures that will
benefit generations of roadway users
as we move into the future. ■
Above: The variation
in traffic signs
around the world –
including between
Europe and the
United States –
makes consistent
and accurate
detection more
difficult
Traffic signs need to accommodate the needs of all road users,
including those without the technology, through all stages of
autonomous vehicle deployment. Agencies have a clear path on signing
improvements to prepare for tomorrow’s technology