Road Signs Perception: Eye Tracking Case Study in Real Road

Traffic

Kateřina Bucsuházy

1,2

, Michal Belák

, Vendula Gajdůšková

and Robert Zůvala

Institute of Forensic Engineering, Brno University of Technology, Brno, Purkyňova 118, Czech Republic

Transport Research Centre, Brno, Líšeňská 33a, Czech Republic

Keywords: Eye Tracking, Road Sign, Advertisements, Road Safety, Perception, Driving.

Abstract: This study investigates driver visual perception of road traffic signs under real road conditions. Using mobile

eye tracking technology, we analyzed glance behavior toward various traffic signs and advertisements along

urban and highway routes during daytime and nighttime conditions. Results showed significant differences in

glance duration and frequency based on sign type, environmental conditions, and the presence of

advertisements. Drivers primarily focused on speed limit and directional signs, while advertisements attracted

longer glance durations despite their lower frequency of detection. Nighttime conditions generally led to

increased glance durations and higher frequencies for most traffic sign types. These findings highlight the

importance of optimizing road signage design and placement to improve driver attention and road safety,

especially in environments with high visual clutter. Limitations include the exclusion of peripheral vision

effects and potential biases introduced by experimental settings.

1 INTRODUCTION

Road sign perception is a prerequisite to receiving

information on that sign and anticipating it in the

driver's behavior, so knowledge and perception of

traffic signs is necessary for safe driving and

subsequently traffic safety. Traffic signs play

important role in driver – road infrastructure

interaction as they provide important information

about traffic rules, warn before danger or relevant

changes in road environment.

There has been a number of realized research

focused on the road sign perception mainly visual

detection in real road traffic sometimes also in

combination with verbal reports while driving or after

driving (e.g. Topolšek et al., 2016; Costa, 2014;

Inman et al. , 2012) and simulator studies which used

ability to recall a sign after passing it to analyze

perception (e.g. Kuniyoshi, et al., 2021). The

Kapitaniak et al. (2020) based on literature review

concluded that eye tracking currently belongs among

the most frequent methods for the study of cognitive

strategies, mainly visual strategies and enable a

quantitative assessment of objective parameters

under different experimental conditions.

The driver behavior including perception in road

traffic is influenced by various factors such as age

(e.g. Donmez and Liu, 2015; Topolšek and Dragan,

2016), gender (e.g. Cui et al., 2023), location or type

of roadside elements (e.g. Crundall et al., 2006;

Bucsuházy et al., 2018), weather condition or daytime

period (Mohamed et al., 2013). However, the

conclusions of studies focusing on behavior in

different situations or the visual perception of

different elements in road traffic often differ with

regard to the definition of influencing factors.

Topolšek et al. (2016) also point out that drivers

could have difficulties differentiating relevant and

irrelevant information for safe driving such as traffic

signs and advertisements. Hudák and Madleňák

(2016) also shows that the driver missed 60% of

traffic signs. The advertisements do not provide any

relevant information for the safe driving so negatively

affect driver attention, increase mental workload and

reduce ability to safe driving (Edquist et al., 2011;

Salaheddine et al., 2010; Bucsuházy et al., 2018;

Smiley, 2005). Some of the previous studies (e.g.

Seppelt et al., 2017; Hudák and Madleňák, 2017;

Dingus et al., 1989) also emphasize that off road

glances longer than 2 second can lead to critical

situations.

In previous studies, the authors focused on the

glancing towards billboards (e.g. Bucsuházy et al.,

2019). Elements near the road attract the driver's

attention and their correct and timely understanding

228

Bucsuházy, K., Belák, M., Gajd ˚ušková, V. and Z˚uvala, R.

Road Signs Perception: Eye Tracking Case Study in Real Road Trafﬁc.

DOI: 10.5220/0013481000003941

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 11th International Conference on Vehicle Technology and Intelligent Transport Systems (VEHITS 2025), pages 228-234

ISBN: 978-989-758-745-0; ISSN: 2184-495X

and interpretation are important for road safety. A

complex and not entirely clear combination of

multiple traffic signs can be confusing and potentially

lead to traffic accidents.

The recommendations for countermeasures to

increase road safety, as described by Nordqvist et al.

(2023), also include removing superfluous signs and

consolidating the existing signs to reduce visual

clutter and improve driver attention.

Our study investigates how different types of

signs and environmental conditions affect visual

attention. The study aimed to analyse driver visual

perception of vertical traffic signs under real traffic

conditions focusing on:

 Analysis of glances towards different types of

road signage.

 Comparison of visual attention focused on

traffic signs and advertisements (mainly

billboards).

 Analysis of visual attention during daytime and

nighttime conditions.

Based on the literature review was assumed that:

 The glances toward vertical traffic signs are

influenced by the type of traffic sign.

 The visual perception of advertisements and

road signs differ significantly.

 Drivers perceive differently in nighttime and

day-time conditions.

2 METHODS

2.1 Experiment

The study was conducted in real road traffic. The

analysis included one test route in city of Brno and

one test route around city of Vyškov (including

highway section and city of Vyškov). The first test

route (in the Brno city) was 16 km length, and second

test route (highway and Vyškov city) was 75 km

length. Both test routes include variety of driving

situations. Measurements were carried out under

similar weather conditions (without rain or fog)

during daytime and nighttime condition.

The study included men drivers (n=16) aged from

20 to 50 years, who are active drivers. Drivers were

selected among volunteers that responded to the

participation invitation. All participants were free of

medical or cognitive disabilities (including visual or

auditory disabilities, due to eye tracking limitations,

drivers suffering eye disease were excluded from the

dataset). Every participant drove for two driving tests

– first during day and second during night in the same

city. The drivers were not familiar with the aim of the

study and test track itself. The participants were

distributed on two test tracks – in the city of Brno, and

in the city of Vyškov and its surroundings. Two

drives need to be excluded due to the eye tracking

technical issues and data losts. Drivers were

instructed to drive on predeterminated route using

navigation system with audio-visual feedback. Both

experiments were realized with instrumented vehicle

of IFE BUT – BMW 5 equipped with modern safety

systems.

All participants completed provided written

informed consent. Before the experiment, the safety

procedure and basic instructions including the

information about the equipment and also the vehicle

itself was introduced to all participants. All

participants were accompanied by 3 researchers – one

researcher at vehicle front seat ensured the safety and

researchers at back seat control the experiment (make

notes and ensure system function).

2.2 Eye Tracking

The analysis of visual behavior was realized using

mobile eye-tracking. The video-based mobile eye

tracker Dikablis Glasses 3 was used. Dikablis Glasses

3 (Ergoneers) eye tracker is binocular with eye

cameras tracking frequency 60 Hz and resolution 648

x 488 pixels. The scene camera resolution is 1920 x

1080 with tracking frequency 30 fps (manual Dikablis

Glasses). The Dikablis Glasses are connected directly

to the recording computer during drive, the data were

observed by accompanying researcher in the vehicle

during driving.

The glance behavior analysis was conducted using D-

Lab software. Each video was analysed frame by

frame to assess if the participant visually detected the

sign (respectively advertisement) and also to analyse

the length of the glance if the element was visually

perceived.

2.3 Road Sign Classification

The Vienna Convention on Road Signs and Signals

(United Nations Economic & Social Council, 1968)

presented main categories of road signs: danger

warning signs, regulatory signs including priority

signs; prohibitory or restrictive signs; mandatory

signs; special regulation signs and informative signs

including information, facilities or service signs;

direction, position or indication signs and additional

pannels. In Czechia, the regulation 294/2015

described among others vertical traffic signs and its

classification in Czechia: warning sign (mainly

Road Signs Perception: Eye Tracking Case Study in Real Road Trafﬁc

229

triangular), yield signs, prohibitory signs (mainly

circular), mandatory signs and informative signs.

Based on these categories were classified existing

road signs on test tracks with respect to its frequency

on analysed track, so following categories were

analysed:

 Warning sign (mainly triangular)

 Yield signs divided to main road sign and

stop/give way signs

 Prohibitory signs (mainly circular) divided to

speed limit signs and other prohibitory signs

 Mandatory signs mainly direction signs

 Informative signs divided to direction signs,

zebra crossing sign and other information signs

The road signage perception was compared with

the perception of advertisements on test track

(including all types of advertisements such as

billboards, bigboards, megaboards).

2.4 Visual Perception of Vertical Road

Signs

Three main objectives were studied in the experiment

– visual perception of road signs, comparison of

visual perception towards vertical traffic signs and

advertisements and comparison of visual perception

during daytime and nighttime conditions. The

analysis was focused on glances towards signage

which included glance shift off the road toward the

vertical traffic sign and its visual fixation.

The descriptives confirmed the hypothesis that the

length of glances towards vertical traffic signs are

influenced by the type of traffic sign. The differences

are also confirmed by statistical analysis (Kruskal-

Walis non-parametric test).

With respect to frequency, drivers predominantly

glanced towards speed limit signs (21%), informative

signs such as direction signs (22%), and main road

yield signs (19%). The percentage of fixations on

various types of traffic signs ranges between 9% and

22%. However, the results should be interpreted

concerning the eye-tracking method limitation. The

method does not allow a comprehensive analysis of

peripheral vision and object detection using

peripheral vision.

Histogram (Figure 1) also illustrates the higher

frequency of glances within the length in the interval

0.4-0.6 s related to mandatory signs and

advertisements. The longest glances are related

mainly to the perception of informative signs namely

direction signs.

The statistical analysis also confirmed the second

hypothesis, that the visual perception of

advertisements and road signs differ significantly.

The pair-wise comparison shows not statistically

significant differences among the advertisement and

informative signs (direction and other types),

mandatory signs and yield signs. The glance length

was statistically significantly different in case of

comparison of advertisement with yield sign – main

road, informative signs – zebra crossing, warning

signs

and prohibitory signs (see Figure 2). Although

Figure 1: Visual perception of vertical traffic signs and advertisements (author).

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230

Figure 2: Visual perception of vertical traffic signs and advertisements (author).

Table 1: Visual perception of vertical traffic signs (author).

Type of signs

Mean

(

)

Median

(

)

Min

(

)

Max

(

)

Yield signs

(

main road

)

0.46 0.41 0.10 1.75 348

Informative

signs

0.54 0.45 0.10 2.39 685

Mandatory

signs

0.54 0.49 0.18 1.33 50

Yield signs

(five way /

stop)

0.50 0.47 0.10 1.44 116

Informative

signs - zebra

crossing

0.44 0.36 0.10 2.26 118

Advertisement 0.56 0.52 0.10 1.97 184

Prohibitory

signs –

limit

0.51 0.45 0.17 1.99 93

Informative

signs –

direction signs

0.63 0.52 0.10 2.38 461

Warning signs 0.45 0.37 0.10 2.41 123

the advertisements rank among the longer off-road

glances, in terms of the frequency, drivers perceived

only about 4% of advertisements on the route.

However, the data may be influenced by the fact that

the drivers drove the borrowed vehicle and were more

aware as they were informed about being monitored.

Visual perception of traffic signage during the

daytime and nighttime conditions is also statistically

significantly different (p-value 0.01) as expected.

Descriptives demonstrate that mean and median

glance lengths on vertical traffic signs were longer at

nighttime conditions. Differences in the perception of

different types of vertical traffic signage are also

more noticeable at night than during the day (Figure

3). In comparison to the daytime drives, at night are

apparent statistically significant differences in the

case of comparison of advertisement with zebra

crossing sign perception, and also informative and

prohibitory signs, mandatory and warning signs,

speed limit signs and warning signs, and the

difference among yield sign – the main road in

comparison to the warning signs and also prohibitory

signs. In the daytime conditions, these described

differences were not statistically significant.

3 DISCUSSION AND

CONCLUSION

One of the crash causes could be the high density of

information which affect the ability to detect relevant

information in road traffic, even potential risk. Road

signs are one of key elements to ensure road safety

and anticipate safe behavior, so we aimed to analyse

visual perception of road signs in real road traffic and

selected factors which could influenced it perception

such as type or daytime. The results could be

beneficial for road infrastructure design and

identification of potential risks in road traffic related

to insufficient perception of a certain type of road

sings by drivers.

The frequency of road signs' visual perception was

surprisingly relatively low - ranging between 10 and

30% perceived road signs. Similarly, Costa (2014)

and Inman (2012) state that visual fixations to vertical

road signs are low. The results obtained in our study

may be influenced by the usage of a navigation

system that draws attention to several traffic signs.

However,

the navigation was chosen to ensure the

Road Signs Perception: Eye Tracking Case Study in Real Road Trafﬁc

231

Table 2: Daytime vs. nighttime visual perception of vertical traffic signs (author).

time Ni

httime

Type of signs

Mean

(s)

Median

(s)

Min

(s)

Max

(s)

Mean

(s)

Median

(s)

Min

(s)

Max

(s)

Yield signs

(

main road

)

0.43 0.40 0.10 1.44 116 0.48 0.42 0.11 1.75 232

Informative signs 0.52 0.44 0.10 2.06 306 0.55 0.47 0.10 2.39 379

Mandatory signs 0.51 0.49 0.18 1.18 25 0.56 0.47 0.22 1.33 25

Yield signs

ive wa

sto

0.44 0.39 0.10 0.93 49 0.55 0.49 0.15 1.44 67

Informative signs –

zebra crossin

0.41 0.36 0.11 1.15 46 0.46 0.36 0.10 2.26 72

Advertisements 0.54 0.49 0.10 1.70 116 0.60 0.54 0.17 1.97 68

Prohibitory signs –

limit

0.50 0.42 0.18 1.22 29 0.52 0.47 0.17 1.99 64

Informative signs –

direction signs

0.59 0.51 0.10 2.12 188 0.65 0.52 0.10 2.38 273

Warning signs 0.48 0.34 0.10 2.41 57 0.43 0.37 0.10 2.04 66

Figure 3: Visual perception of vertical traffic signs and advertisements in daytime/nighttime conditions (author).

comparability of the driving and the instructions

given by the driver during the movement on the set

route.

Costa (2014) also concluded that visual fixations

to vertical road signs are very short (154 ms). Our

study shows that the mean average glance at traffic

signs was around 0.5 s. The significantly higher

values cannot be caused only by the comparison of

different variables - glances (which included not only

fixations but also glance shifts) analyzed in our study

and fixations analyzed by Costa (2014). Longer

visual fixation on traffic signs (300 ms) in

comparison to Costa (2014) was also described by

Sprenger et al. (1999).

The mean glance duration on advertisements in

the road surrounding was 0.6 s in daytime condition

and 0.7 s in nighttime conditions. Previous studies

reported mean glance distraction between 0.4-0.9 s

(Bucsuházy et al., 2014; Smiley et al., 2005;

Misokefalou et al., 2015). In general, drivers

perceived less advertisements – the frequency of

advertisements visual perception was lower in

comparison to the perception of road signs. However,

when drivers look at the advertisements, the glance

length was usually longer in comparison to the

perception of road signs. In contrast, Smiley (2005)

concluded that average glances on advertisements

were similar as those found in studies of traffic signs

(0.5 s). However, Smiley (2005) similarly as number

VEHITS 2025 - 11th International Conference on Vehicle Technology and Intelligent Transport Systems

232

of previous studies did not distinguish between the

types of traffic signs and daytime conditions.

The driver's perception differed concerning the

type of traffic sign and daytime. At nighttime

conditions, traffic sign glances were longer and more

frequent in the case of most types of traffic signs.

While during the daytime drivers glanced at 10-20%

of traffic signs, at nighttime conditions the frequency

of watching traffic signs was higher (between 20-30%

for majority of traffic sign types). In contrast,

Madleňák (2018) reported that drivers followed 21%

of road signs at night and 35% during the day. The

results could be influenced not only by the road sign

type but also by retroreflexivity of road sign, which

was not distinguished in this study. Similarly to what

Madleňák (2018) describes, our results show a lower

frequency of visual attention toward advertisements

during daytime conditions.

The results could be affected by the identical road

track for both experiments, so also identical

advertisements in both conditions (see also

limitations). Also, peripheral vision plays a role in

road sign perception as evidenced by Costa et al.

(2018). However, the eye-tracking method does not

allow a comprehensive analysis of peripheral vision

and object detection using peripheral vision. The

limitation of the eye-tracking method could be also

seen in the fact that seeing does not necessarily lead

to perception. The interpretation of the results needs

to consider the limitation of the eye-tracking method.

Except for the limits resulting from the method

used, the study faced several limitations:

 The drivers were aware of monitoring of their

visual behavior

 Some of the factors such as locality, the change

of driving behavior following the road sign

perception, age, gender, etc. were not subjected

to this study.

 Future studies should also include a control

group, which allows for analysis if the results

are not distorted by the realization on the same

test track at nighttime and daytime conditions.

Future studies should also reflect the

representativeness of the driver population

(including age, gender, different type of road

users).

 The combination of visual perception analysis

with verbal reports while driving or after

driving could be used to increase the validity of

the results, but it should be also analyzed how

these combinations affect results and driving

behavior itself.

High-clutter environments, such as urban areas with

dense roadside advertising and excessive traffic

signage, often overwhelm drivers with competing

visual stimuli (see Fig 4). This visual overload can

lead to delayed or missed recognition of critical

traffic signs, resulting in unsafe driving behavior and

an increased risk of accidents. Additionally, the

overabundance of traffic signs may cause drivers to

omit or overlook relevant information, further

compromising road safety.

Figure 4: Eye tracking record of a driver's gaze at a

dangerous intersection (location of frequent crashes)

(author)

To address these issues, findings suggest that

redesigning the placement of traffic signs in high-

clutter environments could significantly improve

driver attention. Consolidating traffic signs is

essential to reduce their density and visual

complexity. A thorough revision of existing traffic

signs is necessary to identify and eliminate

redundancy, ensuring that only essential information

is conveyed. Furthermore, minimizing or removing

advertisements in the vicinity of roads can help

reduce distractions and improve the overall visibility

of traffic signs. By optimizing the placement and

content of traffic signs, along with addressing visual

distractions in the road environment, it is possible to

create a more navigable and less overwhelming road

traffic infrastructure.

ACKNOWLEDGEMENTS

This article was produced with the financial support

of the Ministry of Transport within the program of

long-term conceptual development of research

organizations and The Ministry of Education, Youth

and Sports.

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233

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