Acta Polytechnica CTU Proceedings https://doi.org/10.14311/APP.2025.52.0100 Acta Polytechnica CTU Proceedings 52:100–108, 2025 © 2025 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague IMPACT OF ILLUMINATED ADVERTISING DEVICES ON ROAD TRAFFIC SAFETY Luboš Nouzovský∗, Zdeněk Svatý, Karel Kocián, Jonáš Maleček Czech Technical University in Prague, Faculty of Transportation Sciences, Department of Forensic Experts in Transportation, Konviktská 20, 110 00 Prague, Czech Republic ∗ corresponding author: nouzovsky@fd.cvut.cz Abstract. This article examines the impact of illuminated advertising devices on road safety in urban environments. By measuring the light parameters of advertising displays and comparing them to public lighting, the study analyzes how the brightness and dynamic elements of these devices affect driver attention, reaction times, and overall ability to perceive traffic situations. The findings indicate that high-brightness, dynamic advertising displays can significantly increase the risk of traffic accidents, especially during nighttime driving. The study also highlights the insufficiency of current legislative regulations, which primarily focus on public lighting systems, and suggests that more comprehensive guidelines should be established to address the specific characteristics of illuminated advertising devices. Two measurement methods were employed: horizontal illumination of roadways and a gradient luminance analysis, both of which provided insights into the disruptive influence of these devices on road safety. The article concludes by recommending specific legislative changes, improved regulation of advertising installations, and the development of further research to better understand the long-term effects of these devices on accident rates. By addressing these challenges, this research aims to contribute to safer road environments and minimize the negative impact of illuminated advertisements on traffic flow and driver behavior. Keywords: Advertising devices, road safety, lighting. 1. Introduction The impact of advertising devices on road safety is still the subject of many new studies and publications in the international scientific research community [1]. The solution to this problem is undoubtedly complex and involves not only the examination of the technical characteristics of the advertising devices, such as their dimensions, positioning in relation to the road, light- ing intensity or the use of dynamic elements, but also the content of the messages presented. The combina- tion of these aspects can lead to the driver’s attention being diverted from the situation on the road to the advertising devices, which increases the risk of road accidents and has a negative impact on road safety. This may result not only in disruption of traffic flow but also in damage to property or serious health risks to road users [2]. For these reasons, a growing num- ber of expert studies and researches are focusing on analysing this issue, trying to clarify the influence of individual factors and proposing possible measures to regulate them, including adjustments to legislative standards. In the urban environment, advertising has long been an integral part of the public realm. Illuminated advertising, especially at night, attracts the attention of drivers and distracts them from the traffic situation. This phenomenon can reduce or interfere with drivers’ attention, increase their reaction time and impair their ability to recognise obstacles or traffic signs in time [3]. Studies show that the brightness and contrast of illuminated advertising compared to road lighting can significantly affect visual field perception and contribute to the risk of road accidents [4]. Given these risks, it is necessary to further investigate the lighting parameters of these devices, such as their intensity, dynamics and positioning, and to find ways to regulate their impact on road safety [5, 6]. This paper focuses on this issue and presents two types of measurements that can be used to assess the impact of illuminated or light-emitting advertising devices. 2. Lighting parameters of advertising devices and their evaluation Driver’s thinking and perception is a complex and intricate system influenced by a number of internal and external inputs. The interaction of a person with a vehicle in relation to a specific traffic situation is primarily determined by the driver’s sensory percep- tion, which enables a person to orient themselves in a given situation. Visual perception is therefore es- sential, as it mediates up to 90 % of the perception of the environment. It is all the more important to ensure that this perception is correct, even in low light conditions, when illuminated signs objectively stand out more than other objects [6]. The Czech Act No. 13/1997 Coll. on Roads states that it is possible to place and operate advertising devices that “do not dazzle the users of the respective 100 https://doi.org/10.14311/APP.2025.52.0100 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en vol. 52/2025 Impact of illuminated advertising devices on road traffic safety road or otherwise interfere with road traffic” [7]. How- ever, the general nature of these restrictions makes them difficult to enforce in some cases. This may be because there are currently no regulations governing the lighting parameters of advertising devices. The closest thing to this are the technical standards CSN EN 13201-1 to 5 [8], which define measurement meth- ods, evaluation and glare classes, but apply to public lighting. For the purpose of the measurements processed and evaluated in cooperation with the company SATHEA VISION s.r.o., advertising devices were included in the public lighting system mainly for the following reasons: • Advertising devices are usually placed in a similar position to the road as the standard public lighting system. • The light sources used for advertising devices are similar to those used for public lighting systems. • A lighting design methodology has been developed to minimise the negative impact on a driver, which is also applicable to advertisements. • Current Czech legislation and technical standards, other than those for public lighting, only marginally address the issue of active adverisements. • The impact of illuminated advertisements on the road can be measured using methods designed to measure the quality of public lighting systems. Two different approaches were used to assess the effect of the luminance of the selected advertisements, namely horizontal road illuminance measurements and gradient luminance analysis. 2.1. Road horizontal illuminance measurement 2.1.1. Measurement procedure Measurements are taken by an automated data collec- tion platform (Figure 1). The platform uses calibrated sensors to measure traffic on three parallel levels in the carriageway. The entire system uses advanced com- pensation for adverse effects and interference. The sampling and processing speed allows measurements to be made in real-time traffic, and the measured data is interpolated to produce a matrix of equidistant points in accordance with the ČSN EN 13201 lighting evaluation standard. The measurement is also depen- dent on road conditions and vehicle manoeuvrability. A Class B hand-held luxmeter was used to verify the measurements (Figure 2). 2.1.2. Locations Measurements were carried out at eight locations (i.e. D1 to D8), which are shown in the following maps and visual overview (Figures 3–5). All sites are located on two streets in Prague, namely Rozvadovská spojka and 5. května. The advertising devices have been selected according to their luminosity and variability Figure 1. SATHEA traffic horizontal illuminance measurement vehicle. Figure 2. Calibration certificate and SONEL luxmeter. 101 L. Nouzovský, Z. Svatý, K. Kocián, J. Maleček Acta Polytechnica CTU Proceedings Figure 3. Location of 5. května street with marked advertising devices [9]. (i.e. dynamics), whereby the advertising media at locations D1 to D6 have dynamically variable content, while the advertisements at locations D7 and D8 are static. 2.1.3. Processing and evaluation Measured data was first interpolated and filtered to give the most accurate picture of illuminance along the road. Data in the direction of one lane were then selected, and was further filtered using a moving aver- age filter with a window of 7 forward and 7 backward samples (the smoothed data is shown in the graphs below). In each graph, the location of the respective advertising device is always marked with a red bar to assess whether the road illuminance is affected at that location. The following figures show locations D8 and D1 as an example see in Figures 6 and 7. The advertisement at the D8 location was the only one found to have a significant effect on the longitu- dinal uniformity of the lighting due to its position directly above the carriageway. All other advertise- ments close to the road were found to have a negligible effect on the longitudinal uniformity of the lighting. Measured data, including the effect of the advertis- ing device on the illuminance, can also be displayed in a heatmap or greyscale spectrum for better illus- tration, as shown in Figure 8. 2.1.4. Summary of horizontal illuminance measurements The data show that the influence of advertising devices in question on the illuminance of the measured sections is minimal and at the level of measurement error. This conclusion was confirmed by manual measurement with a luxmeter, where the change caused by the light emitted by the advertising device was about 10 % of the illuminance on the roadway compared to the state when the advertising was switched off. This is probably due to the orientation of the advertisement, where its normal is approximately parallel to the road. The light rays hit the road at a high angle to the normal of the impact area. Illuminance is a function of the angle of incidence, so the effect is negligible. It should be noted, however, that a light source which does not contribute to the illumination of the road and its surroundings can only be considered as a source of glare with a negative effect on the visual performance of the driver. 2.2. Gradient luminance analysis The purpose of the measurement is to evaluate the brightness of the light sources in the captured scene. For this measurement, the images were converted to grey scale and then rendered in false colours for subjective evaluation. No further adjustments were necessary when the photos were evaluated numerically. 2.2.1. Measurement procedure The measurements were carried out at selected loca- tions in the streets 5. května and Rozvadovská spojka. The optical sensor system was placed according to the requirements of ČSN EN 13201 on a standard ob- server (i.e. at a height of 1.5 m, at a distance of 60 m from the advertising device and with an inclination of the observation plane of 1°). The composition of the scene was such that the advertising device, roads and public lighting fixtures were recorded at a distance of at least 150 m from the advertising device. The images were taken using a Sony ILCE-5000 camera with a 19mm fixed focal length lens. All shooting parameters except the shutter speed were kept constant. The sensitivity (ISO) was set at 100 and the aperture at f14, and the shutter speed was varied from 1/4000 s to 1 s for each scene to find the point at which the sensor operates in the linear range. The three best images were then selected for further processing – the first for subjective evaluation and the other two for objective (numerical) evaluation. The specifics and limitations of the specific mea- surements reported in real-time traffic included the following: • High dynamic scene contrast. ▷ High brightness of an advertising device and lu- minaires. ▷ Luminious flux from an advertising device di- rected at the driver at a more direct angle than public lighting. ▷ Restrictive sensor angles against interfering light. • Sites do not allow fully static measurements. ▷ Dynamic advertisements are switched off at 22:00, a time when there is still a lot of traffic at these locations. 102 vol. 52/2025 Impact of illuminated advertising devices on road traffic safety Figure 4. Location of Rozvadovská spojka street with marked advertising devices [9]. Figure 5. Locations D1 to D8. 103 L. Nouzovský, Z. Svatý, K. Kocián, J. Maleček Acta Polytechnica CTU Proceedings Figure 6. Graph of the horizontal illuminance at the D8 location, showing the influence of the advertising device. Figure 7. Graph of the horizontal illuminance at the D2 location, showing the influence of the advertising device. Figure 8. Heatmap (left) and grey scale (right) data display. ▷ It is not possible to regulate traffic on roads for fully static measurements. 2.2.2. Locations The locations selected for the gradient luminance anal- ysis are identical to those for the horizontal road illu- minance measurements. Due to the financial, organi- sational and data requirements of such measurements, the measurements were carried out at locations D1 and D4 to D7. A subjective expert assessment of illu- minance and the effect of illuminated advertising on drivers was also carried out for the selected locations. 2.2.3. Processing and evaluation Objective assessment The only applicable param- eter for assessing glare on roads is the threshold in- crement (TI), which is a measure of the reduction in visibility caused by the restrictive glare of the lumi- naires in the road lighting system [4]. However, due to the relatively heavy traffic and the time-varying content of the advertisements, it could not be reliably determined. Therefore, the ratio of the equivalent veiled luminance of the public lighting and the sig- nage was used as a proxy for the assessment. Curtain luminance is defined as: Lv = 10Erk ϑ2 [cd · m−2] (1) where • Erk – illuminance at the point of the observer’s eye in a plane perpendicular to the line of sight and inclined by 2°from the horizontal, • ϑ – is the angle formed by the line of sight and the line connecting the observer’s eye and the source of glare. The most significant fixed source of glare on roads is public lighting. The equivalent veil luminance of the 104 vol. 52/2025 Impact of illuminated advertising devices on road traffic safety Figure 9. Angle comparison between an advertising device and a public lighting luminaire. public lighting system was therefore used as a reference ilustrated in Figure 9. If the equivalent luminance did not exceed the reference luminance, the advertisement was considered to be an insignificant source of glare in relation to the public lighting sources already installed and meeting the requirements of ČSN EN 13201. Luminaires between 30 and 300 metres from the monitoring site were included in the assessment. The luminaires are marked L1P (nearest luminaire to the right of the road), L1L (nearest luminaire to the left of the road), L2P (second nearest luminaire to the right of the road), etc. The marking of an advertising device corresponds to the marking of the same advertising device on the map. Two locations have been used as examples, namely D5 and D6, whose values are given in detail (see Table 1 and 2). The second column indicates the angle in degrees between the plane of observation and the junction of the light source and the camera lens. The solid angle indicates how much of the total field of view is occupied by a given light source. The average illuminance of an object is the calculated value of the luminous intensity of each pixel of the image that falls within the space of a given light source. The relative horizontal illuminance produced by a given source corresponds to the average brightness of the object, angle and solid angle according to the relationship: E = L cos ϑ τ [lx] (2) where • L – average brightness of the object – the value of the luminous intensity of each pixel of the image belonging to the area of the light source, • ϑ – is the angle formed by the plane of observation and the junction of the light source and the camera lens, • τ – solid angle – the size of the object in the field of view. Table 3 shows the resulting luminance analysis val- ues. The veiling luminance of public lighting is the sum of all individual luminances. The veiling lumi- nance of an advertisement is, as the name suggests, the veiling luminance induced by the advertisement. The main indicator of glare is the ratio of the veiling luminance of the advertisement to the sum of the veiling luminances induced by the public lighting lu- minaires. The higher the value, the more significant the glare caused by the advertising device compared to the glare caused by the public lighting system. The results show that one of the advertising de- vices significantly exceeds the luminance values of the public lighting system. However, such a result does not justify the claim that the advertisements do not comply with the current standard for street light- ing. However, it can be stated that the technology used is capable of exceeding the permitted values for public lighting by several times in terms of radiated brightness. Subjective assessment This assessment consideres the overall situation at the selected locations and the impact of the advertisements on drivers in relation to other objects and the overall road environment. The aim is to provide a comprehensive picture of the situation at the measured locations in terms of visual presentation. As a result, the sites were classified into three levels according to their impact on drivers, as shown in the situations below: Advertisement with a minimal subjective im- pact on the observer The advertisements at D1 and D4 locations are so unobtrusive within the overall brightness of the scene that their impact on the driver is minimal. Subjec- tively, there is little or no glare to the driver. Advertisement with an average subjective impact on the observer For D6 and D7 advertising devices, the effect on the driver depends mainly on the content displayed in terms of the colours used and the intensity of the brightness. Advertisement with a high subjective impact on the observer The advertisement at D5 location is a high-brightness device. Within the overall bright- ness of the scene, it stands out significantly above the brightness of other light sources and the brightness of the road. In this comparison, it is clear that the ambient scene values around the billboard, in par- ticular the road surface, are close to zero. Such an effect is undesirable because the driver, whose vision is adapted to the high brightness of the billboard, does not have sufficient reserve to distinguish less bright details on the road. This increases the likelihood of missing an obstacle, confusing information from ver- tical road markings and similar undesirable features. Situations are shown in Figure 10. 2.2.4. Summary of brightness analysis results The advertisements and locations that were most suit- able for evaluation in terms of road geometry, lumi- naires and mast heights were selected to determine the impact of illuminated advertising on drivers. The measurements show that individual advertisements vary in both brightness and position in the field of view. The equivalent veiled luminance of D1 and D4 is less than the equivalent veiled luminance of the public lighting, whereas for D6 and D7 it is close to this value. In the case of sign D5, the measured 105 L. Nouzovský, Z. Svatý, K. Kocián, J. Maleček Acta Polytechnica CTU Proceedings Light Source Angle ϑ Solid Average Relative Horiz. Relative Veil Angle τ Brightness Illuminance E Brightness Lv of the Object L [°] [sr] [cd m−2] [lx.sr] [cd sr m−2] Luminaire L1P 16,328 0,000036 4655,62 0,16301 0,00611 Luminaire L1L 14,261 0,000027 4873,28 0,12627 0,00621 Luminaire L2P 9,412 0,000011 3286,72 0,03586 0,00405 Luminaire L2L 8,944 0,000006 1680,84 0,00992 0,00124 Luminaire L3P 6,487 0,000002 719,62 0,00154 0,00037 Luminaire L3L 6,708 0,000004 2286,08 0,00976 0,00217 Luminaire L4P 5,278 0,000003 2334,78 0,00658 0,00236 Luminaire L4L 5,421 0,000002 1486,98 0,00365 0,00124 Luminaire L5P 4,615 0,000002 1293,12 0,00297 0,00140 Luminaire L5L 4,628 0,000003 839,88 0,00250 0,00117 Advertisement D 5 5,850 0,002111 545,22 1,14520 0,33463 Table 1. Brightness analysis readings for D5 location. Light Source Angle ϑ Solid Average Relative Horiz. Relative Veil Angle τ Brightness Illuminance E Brightness Lv of the Object L [°] [sr] [cd m−2] [lx.sr] [cd sr m−2] Luminaire L1P 23,179 0,000025 6662,016 0,15570 0,00290 Luminaire L1L 22,815 0,000027 1546,912 0,03857 0,00074 Luminaire L2P 10,79 0,000005 5611,392 0,02601 0,00223 Luminaire L2L 10,647 0,000018 1968,32 0,03417 0,00301 Luminaire L3P 6,994 0,000005 3054,56 0,01399 0,00286 Luminaire L3L 6,903 0,000004 713,792 0,00267 0,00056 Luminaire L4P 5,135 0,000003 1131,392 0,00349 0,00132 Luminaire L4L 5,018 0,000002 282,176 0,00065 0,00026 Luminaire L5P 4,056 0,000002 1788,352 0,00411 0,00250 Luminaire L5L 4,004 0,000001 269,344 0,00034 0,00021 Luminaire L6P 3,315 0,000001 537,344 0,00067 0,00061 Luminaire L6L 3,25 0,000002 776,256 0,00126 0,00119 Luminaire L7P 2,769 0,000001 328,544 0,00026 0,00034 Luminaire L7L 2,704 0,000001 465,792 0,00044 0,00060 Luminaire L8P 2,314 0,000001 432 0,00041 0,00076 Luminaire L8L 2,288 0,000001 588,448 0,00055 0,00106 Advertisement D6 4,251 0,001126 25,831 0,02901 0,01606 Table 2. Brightness analysis readings for D6 location. Location Veiled Luminance Veiled Luminance Ratio of Veil of Public Lighting of Advertisement Luminance (Ad./PL) Location D1 0,039 0,012 0,307 Location D4 0,029 0,018 0,620 Location D5 0,026 0,335 12,717 Location D6 0,021 0,016 0,759 Location D7 0,031 0,029 0,935 Table 3. Results of the brightness analysis of D1, D4, D5, D6 and D7 locations. 106 vol. 52/2025 Impact of illuminated advertising devices on road traffic safety (a). D1 (b). D4 (c). D6 and D7 (d). D5 Figure 10. Brightness analysis in false colour. values were significantly higher than the public light- ing illuminance. On the basis of these measurements, with such a result, it cannot be said that some ad- vertisements violate the current standard for street lighting ČSN EN 13 201. However, it can be stated that, thanks to the progress made in the development of LEDs, advertisements can achieve luminance values that are not negligible at night, but on the contrary can exceed the luminance of the permitted fixed light sources (i.e. public lighting) many times over. The luminous intensity of some advertisements is significantly higher than that of other light sources. This increases the adaptive brightness of the scene for the driver. Compared to the brightness of the road, which is several orders of magnitude lower, this increases the risk of missing an obstacle, reduces the driver’s visual performance and increases reaction time. A particular phenomenon that occurs in the case of an active advertising device with variable content (i.e. a dynamic advertising device) is the change in panel brightness over time. Currently, all legislation relating to street lighting only deals with fixed, constant lumi- nous sources. No methodology has been developed to assess lighting systems with time-varying parameters. However, it should be noted that, from a physiological point of view, two undesirable phenomena occur. The first is a sudden change in the brightness of the screen, which can cause blinding glare or at least a significant reduction in visual performance for a short period of time. The second is a reflex associated with peripheral vision. When there is a sudden change in peripheral brightness, a reflexive withdrawal of attention from the stimulus occurs (i.e. the hazard response). These phenomena can pose a greater hazard than glare from fixed sources of constant luminous flux [10]. 3. Conclusions The results of the measurements confirm that adver- tisements, especially those with high brightness and dynamic content, can have a negative impact on road safety. However, this was not clearly demonstrated for all the selected samples. The brightness and contrast of advertisements distract drivers from the traffic situ- ation, which can lead to longer reaction times and an increased risk of accidents. Based on the results of this study, it can be concluded that the current legislation in the Czech Republic, which focuses on roads, traffic or the lighting system, does not sufficiently cover the specifics of illuminated and light-emitting advertising devices. Therefore, it would be more than appropri- ate to adopt more specific legislative measures that take into account not only static but also dynamic advertising devices and set limits on their brightness, dynamics and positioning. Advertising can be identified as a source of discom- forting glare. No positive effects of advertising devices on road safety or visual comfort of drivers have been 107 L. Nouzovský, Z. Svatý, K. Kocián, J. Maleček Acta Polytechnica CTU Proceedings identified as part of the classification of advertising devices as part of the public lighting system. The pur- pose for which such light sources are installed differs from that of public lighting systems. The light sources of the advertising devices mea- sured are not optically modified in any way to improve the visual comfort of the driver (shading, direction of light flow, etc.). However, public lighting luminaires must be adapted in this way. In particular, the abso- lute value of the luminance of the advertisement and the subsequent calculation of the threshold increment is a parameter that would allow the advertisement to be classified as technically unsatisfactory in the light of current legislation. References [1] J. Hinton, O. Oviedo-Trespalacios, B. Watson, N. Haworth. Beyond the billboard: A review of other external sources of driver distraction. Accident Analysis & Prevention 208:107771, 2024. https://doi.org/10.1016/j.aap.2024.107771 [2] Czech Republic. Ministry of Transport. BESIP Strategy 2021–2030, 2020. [2024-08-11]. https://besip.cz/Besip/media/Besip/data/web/ Strategie-BESIP-2021-2030.pdf [3] K. Bucsuházy, M. Semela, M. Belák, et al. Analysis of selected off-road glances during driving in real road traffic. Transportation Research Procedia 45:580–586, 2020. Transport Infrastructure and systems in a changing world. Towards a more sustainable, reliable and smarter mobility. TIS Roma 2019 Conference Proceedings. https://doi.org/10.1016/j.trpro.2020.03.054 [4] T. A. Dingus, F. Guo, S. Lee, et al. Driver crash risk factors and prevalence evaluation using naturalistic driving data. Proceedings of the National Academy of Sciences 113(10):2636–2641, 2016. https://doi.org/10.1073/pnas.1513271113 [5] T. Blodek, P. Vrtal, T. Kohout, et al. Verification of night road safety inspection by luminance analysis. In 2024 24th International Scientific Conference on Electric Power Engineering (EPE), pp. 1–5. 2024. https://doi.org/10.1109/EPE61521.2024.10559538 [6] R. Brome, M. Awad, N. M. Moacdieh. Roadside digital billboard advertisements: Effects of static, transitioning, and animated designs on drivers’ performance and attention. Transportation Research Part F: Traffic Psychology and Behaviour 83:226–237, 2021. https://doi.org/10.1016/j.trf.2021.10.013 [7] Parliament of the Czech Republic. Act No. 13/1997 Coll. 1997. [8] ČSN 13 201-1,2,3,4,5 (1.10.2024), Osvětlování pozemních komunikací [In Czech; Street lighting]. ČNI Praha. [9] Google. Maps. [2024-08-11]. https://www.google.com/maps [10] L. Nouzovský, P. Vrtal, T. Kohout, Z. Svatý. Using the eye tracking method to determine the risk of advertising devices on drivers’ cognitive perception. Applied Sciences 12(13):6795, 2022. https://doi.org/10.3390/app12136795 108 https://doi.org/10.1016/j.aap.2024.107771 https://besip.cz/Besip/media/Besip/data/web/Strategie-BESIP-2021-2030.pdf https://besip.cz/Besip/media/Besip/data/web/Strategie-BESIP-2021-2030.pdf https://doi.org/10.1016/j.trpro.2020.03.054 https://doi.org/10.1073/pnas.1513271113 https://doi.org/10.1109/EPE61521.2024.10559538 https://doi.org/10.1016/j.trf.2021.10.013 https://www.google.com/maps https://doi.org/10.3390/app12136795 Acta Polytechnica CTU Proceedings 52:100–108, 2025 1 Introduction 2 Lighting parameters of advertising devices and their evaluation 2.1 Road horizontal illuminance measurement 2.1.1 Measurement procedure 2.1.2 Locations 2.1.3 Processing and evaluation 2.1.4 Summary of horizontal illuminance measurements 2.2 Gradient luminance analysis 2.2.1 Measurement procedure 2.2.2 Locations 2.2.3 Processing and evaluation 2.2.4 Summary of brightness analysis results 3 Conclusions References