Low emission zones and their adaptability to small and medium-sized cities

1 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Curso: 2024-2025 Director/Directora: Llano Castresana, Urtzi Estudiante: Zabalegui Calderon, Nerea LOW EMISSION ZONES AND THEIR ADAPTABILITY TO SMALL AND MEDIUMSIZED CITIES MÁSTER UNIVERSITARIO EN DIRECCIÓN DE PROYECTOS TRABAJO FIN DE MÁSTER Fecha: Donostia, 02, julio, 2025 2 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Abstract (English) Through this thesis the adaptability of Low Emission Zones in small and medium-sized European cities will be explored, with an especial focus on the Spanish case. Despite the popularity of such measures as a key strategy to combat urban pollution, current legislation and guidelines follow a one-size-fits-all approach, which creates adaptation challenges for smaller cities. Following a bibliometric review, a comparative analysis between the two types of cities and three case studies, this project identifies clear variations in the design and planning processes, stakeholder participation and complementary measures associated with Low Emission Zones. The results show that smaller cities benefit from more holistic and participatory strategies, but that national guidelines, such as the Spanish, promote a strict approach that is not easily adapted to local realities. Key words: Low Emission Zones / Small and Medium-sized Cities / Sustainable Urban Mobility Abstract (Euskera) Tesi honen bidez, Europako hiri txiki eta ertainetako Isuri Gutxiko Eremuen moldagarritasuna aztertuko da, Espainiako kasuan arreta berezia jarriz. Horrelako neurriek hiri kutsadurari aurre egiteko funtsezko estrategia gisa duten ospearen arren, egungo legediak eta gidalerroek ikuspegi bakarrari jarraitzen diote, eta horrek hiri txikietara egokitzeko erronkak sortzen ditu. Berrikuspen bibliometrikoa, bi hiri moten arteko azterketa konparatiboa eta hiru kasu-azterketa egin ondoren, proiektu honek aldaketa nabarmenak identifikatzen ditu diseinu eta plangintza prozesuetan, alderdi interesdunen parte-hartzean eta Isuri Gutxiko Eremuei lotutako neurri osagarrietan. Hiri txikiek estrategia holistikoagoak eta parte-hartzaileagoak dituzte, baina gidalerro nazionalek, Espainiakoak kasu, tokiko errealitateetara erraz egokitzen ez den ikuspegi zorrotza sustatzen dute. Gako hitzak: Isuri Gutxiko Eremuak / Hiri Txiki eta Ertainak / Hiri Mugikortasun Iraunkorra 3 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Abstract (Castellano) A través de esta tesis se explorará la adaptabilidad de las Zonas de Bajas Emisiones en ciudades europeas pequeñas y medianas, con especial atención al caso español. A pesar de la popularidad de este tipo de medidas como estrategia clave para combatir la contaminación urbana, la legislación y las directrices actuales siguen un enfoque único, lo que crea retos de adaptación para las ciudades más pequeñas. Tras una revisión bibliométrica, un análisis comparativo entre los dos tipos de ciudades y tres estudios de caso, este proyecto identifica claras variaciones en los procesos de diseño y planificación, la participación de las partes interesadas y las medidas complementarias asociadas a las Zonas de Bajas Emisiones. Los resultados mientras que las ciudades más pequeñas se benefician de estrategias más holísticas y participativas, pero que las directrices nacionales, como la española, promueven un enfoque estricto que no se adapta fácilmente a las realidades locales. Palabras clave: Zonas de Bajas Emisiones / Ciudades Pequeñas y Medianas / Movilidad Urbana Sostenible 4 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Table of Contents 1. INTRODUCTION ............................................................................................................................ 6 2. CONTEXT AND MOTIVATION ................................................................................................ 10 3. GOALS AND SCOPE ................................................................................................................... 12 4. BENEFITS OF THE MASTER THESIS ................................................................................... 14 5. STATE OF THE ART .................................................................................................................. 16 a. BIBLIOMETRIC ANALYSIS ...................................................................................................... 16 b. LITERATURE REVIEW ............................................................................................................. 19 6. RESEARCH DESIGN ................................................................................................................... 22 7. LEZ IMPLEMENTATION IN SMSC ......................................................................................... 28 8. LEZ IMPLEMENTATION IN LARGE CITIES ........................................................................ 36 9. COMPARATIVE ANALYSIS ................................................................................................... 41 10. SPANISH GUIDELINES ...................................................................................................... 46 11. CASE STUDY: BASQUE CITIES ....................................................................................... 50 a. CASE STUDY I: BILBAO ......................................................................................................... 51 b. CASE STUDY II: DONOSTIA .................................................................................................. 52 c. CASE STUDY III: VITORIA-GASTEIZ ................................................................................. 53 d. CONCLUSIONS .......................................................................................................................... 54 12. DISCUSSION AND RESULTS ............................................................................................ 56 a. QUANTITATIVE COMPARISON OF POPULATION AND AREA ............................... 56 b. GOOD PRACTICES GUIDE ..................................................................................................... 59 c. ASPECTS TO BE IMPROVED ................................................................................................ 62 d. DISCUSSION ............................................................................................................................... 66 13. CONCLUSIONS...................................................................................................................... 68 BIBLIOGRAPHY .................................................................................................................................. 70 5 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Table of Figures Figure 1. Sign that announces the Environment Zone in Sweden. Source: Buss magasinet ................................................................................................................................................ 6 Figure 2. Research design steps .................................................................................................. 27 Figure 3. Map of the LEZ in Aachen. Source: CLARS ............................................................ 29 Figure 4. Map of the LEZ in Ghent. Source: Persruimte Stad Gent ................................. 31 Figure 5. Map of the LEZ in Freiburg. Source: CLARS ......................................................... 33 Figure 6. Map of the LEZ in Madrid. Source: Avis ................................................................. 36 Figure 7. Map of the LEZs in Stockholm. Source: CLARS ................................................... 38 Figure 8. Map of the LEZ in Amsterdam. Source: CityLogistics ...................................... 40 Figure 9. Delimitation of the LEZ in Bilbao. Source: Ayuntamiento de Bilbao .......... 57 Figure 10. Delimitation of the LEZ in Vitoria-Gasteiz. Source: Ayuntamiento de Vitoria .................................................................................................................................................... 57 Figure 11. Delimitation of the LEZ in Donostia-San Sebastián. Source: Ayuntamiento de San Sebastián .................................................................................................. 57 Table of Graphs Graph 1. Results by category for the search "Low Emission Zone". Source: Web of Science ................................................................................................................................................... 17 Graph 2: Results by year of publication for the "LEZ" term. Source: SCOPUS .......... 18 Graph 3: Results by country for the search "small and medium-sized cities AND emission reduction". Source: Web of Science ........................................................................ 19 Table of Tables Table 1. Final list of SMSCs that appear in published articles. Source: CLARS/Eurostat ................................................................................................................................ 24 Table 2. Comparison between large-sized cities and small and medium-sized cites .................................................................................................................................................................. 45 Table 3. Examples of Low Emission Zones. Source: Spanish Guidelines ..................... 47 Table 4. Population and area affected by the LEZ in Bilbao, Donostia-San Sebastián and Vitoria-Gasteiz. Source: ING ................................................................................................. 57 6 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 1. INTRODUCTION The sudden popularity of Low Emission Zones (LEZ) responds to an increase in awareness over the high levels of air pollution found in most urban areas around the world, both big and small. According to the European Environment Agency (2025), vehicles and other modes of transportation are responsible for a quarter of the European Union´s greenhouse emissions. As a result, measures to reduce traffic related emissions, such as Low Emission Zones, have become a predominant strategy for national governments. However, LEZs have not always enjoyed such an open reception and acceptance. While emission reducing measures may seem a recent concern, the first European Directive on air quality assessment and management was passed on the 27 th of September 1996 (1996/62/EC), focusing on studying the levels of air pollution and on implementing measures to reduce emissions (Council of the European Union, 1996). Nevertheless, that initial regulation had little adherence in the Member States. Sweden was the outlier. That same year, three Swedish cities; Stockholm, Gothenburg and Malmö, implemented “ Miljözon” or Environmental Zones. These zones limited the ability of certain vehicles, those with high emission levels, to enter areas of the cities that were especially sensitive to air pollution (Rapaport, 2002). Those Environmental Zones would take the name of Low Emission Zones in other European states. However, it would not be until the second decade of the new century when other national and regional governments would realize the benefits of emission reducing measures (Ku et al., 2020). In 2008, the second and most influential European Directive was passed, Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe, which established thresholds for multiple gas concentrations, such as sulphur dioxide or carbon monoxide. It is especially Figure 1. Sign that announces the Environment Zone in Sweden. Source: Buss magasinet 7 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO significant as surpassing the established limits impels cities to enact emission reduction measures (Council of the European Union, 2008). Despite the multiple European directives and regulations enacted at the beginning of the century, Member States displayed diverse levels of willingness to implement pollution reduction or mobility restriction measures. After Sweden, Italy and Germany became precursors on the application of Low Emission Zones: Rome´s was established in 2001 whilst Berlin and Milan implemented theirs in 2008 (Ku et al., 2020) (Aydin & Rauck, 2022). Others, such as the French and Spanish governments, were more reluctant to establish them. It would not be until the latter years of the 2010s and the first years of the following decade that the obligation of establishing LEZs was approved by more national parliaments, as was the case of Paris and Madrid in 2021 (Holman et al., 2015) (Lebrusán & Toutouh, 2020). Although the European regulatory framework standardized significant aspects of the emission reduction measures, most importantly, the allowed concentration thresholds, and the national laws rule over the basic characteristics of Low Emission Zones, such as the types of vehicles allowed or the implementation calendar, the initial and planning phases fall under the authority of municipalities or regions (Holman et al., 2015). Thus, local governments are confronted with a project that challenges the functioning of the city, to boot, one with little flexibility and autonomy, especially for smaller cities. Currently, there are more than two hundred European cities that have already implemented or are in the process of designing a Low Emission Zone. This means that two hundred local governments are trying to adapt a policy created in Brussels to the needs and characteristics of their cities (CLARS, 2025). The European and national legislation and guidelines adopt a one-size-fits-all approach, which does not to reflect the particularities of cities, especially of those of smaller size and relevance. Such approach favours cities with big populations, as they concentrate a large share of the population, and in this case, are usually the most urgent cases. Thus, excluding small and medium-sized cities (SMSC) which have different needs and 8 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO concerns. The goal of this thesis is to analyse the adaptability of Low Emission Zones to the diverse needs of smaller cities, all while responding to a simple question: Are Low Emission Zones and the regulations that support them suited to meet the needs and characteristics of small and medium-sized cities? Several steps will be taken in order to answer this apparently simple questions. First of all, a brief context will be provided, centred on the motivation and the goals behind this thesis. Later, the benefits and relation of the thesis with the Sustainable Development Goals will be discussed, with the objective of providing a view on how the results found can be helpful to build a more sustainable and green future. Afterwards, the state of the literature will be examined, as to provide an understanding of previous findings by other researchers and to point out the gaps that this thesis is intending to cover. The review of the literature will show the under-representation of published articles related to analysing the initial and planning phases of Low Emission Zones, especially concerning small and medium-sized cities. Having identified the gaps in the literature, a specific research design will be established, which will determine how the main question will be answered. The initial analysis will consist of a qualitative, comparative analysis between previously established LEZ, both in SMSCs and in big cities. It will focus on the initial and design phases, on how the establishment of the Low Emission Zone was decided and on what steps were taken to adapt the city to the new measure. After extracting the main differences between both types of municipalities, a comparative study will be conducted, with the aims of findings side by side comparisons of certain characteristics, such as stakeholder involvement and the use of complementary measures. Next, the Spanish national guidelines for the creation and management of LEZs will be examined, considering the conclusions extracted from the previous analysis. The last part of the analysis will consist of the examination of three case studies: Bilbao, Donostia-San Sebastían and Vitoria-Gasteiz. These cities have recently or are shortly going to implement a LEZ following the guidelines provided by the Spanish government. The goal will be to check if the real 9 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO application of the guidelines results in a personalized implementation the Low Emission Zone. To gather all the information collected through the research section of the thesis, a results and discussion part will be produced. In three subsections, this part will explore the quantitative effects of LEZs in small and medium-sized cities; gather a good practices guide and identify the major weaknesses of previous initial and planning processes. The conclusion will be used not only to provide a final answer to the research questions, but also to examine the limitations and future implications of this research. 16 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 5. STATE OF THE ART Before conducting the research to find whether the current approach to designing a Low Emission Zone adapts to the needs of small and medium-sized cities, the current state of the academic literature must be analysed. This next section is divided into two parts. In the first one, a bibliometric analysis will be conducted. The goal is to understand in quantitative terms the characteristics of the published articles. On the other hand, the second section will explore the topics and findings of the previously identified literature. The aim of this section is to identify both the basis and the gaps that this thesis will try to cover. a. BIBLIOMETRIC ANALYSIS In order to understand how significant the gap in the research of Low Emission Zones is, most specifically in terms of small and medium-sized cities, a bibliometric analysis has been conducted. For this study, metrics have been obtained from two websites: Web of Science and Scopus. They have been chosen because they provide an analysis of the different characteristics of the literature, such as origin of the paper, date and subject area. Other search engines have been omitted because of a lack of filtering criteria. As it will be explained below, the results of the analysis show a clear under-representation of small and medium-sized cities compared to bigger metropolis. The examinations conducted on Web of Science and Scopus show almost identical results. First of all, the term “Low Emission Zone” is too broad of a term to function as a base, with over 24.000 articles found in the first engine and 11.500 in the second one. Moreover, not only were the number of articles unsustainable but the topics that they deal with were ineffective for the goals of this paper, as the search includes articles not related to LEZ. This can be seen in Graph 1, where papers related to natural sciences are the dominant topics. After adding the term “Europe” to the search to concentrate the results to the target territory, the results showed a significant reduction in the number of articles, although the topics continue to be too diverse. 17 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Graph 1. Results by category for the search "Low Emission Zone". Source: Web of Science As it was established that using the full name does not yield the desired results, a different approach was chosen. The initials “LEZ” were, thus, introduced. The reason behind the election of the initials was based on the fact that any articles examining Low Emission Zones would, in the first paragraph, establish “LEZ” as an alternative name for the concept, one that would be used throughout that same paper in an interchangeable manner. This way, the search eliminated any articles that deal with emissions but not with Low Emission Zones. With this new approach, the results were more adequate for an in-depth analysis, as the scope was reduced to less than a 100 articles per search. Any variation of the term “LEZ”, such as “Low Emission Zone(s) LEZ” or “LEZs” showed similar results as the original. First of all, all three revealed an upward trend in relevance starting in the early 2010s, with a peak in the 2022-2024 period, which indicated that it is a highly pertinent topic nowadays, as it can be seen in Graph 2. Secondly, the articles were no longer mostly about natural sciences, but other topics gained importance, such as public health and public transportation. Lastly, an analysis of the countries of origin of the articles showed that the research into Low Emission Zones is a mainly European topic, with Spain, Germany and the United Kingdom as the main contributors. Out of the top ten countries, only three were non-European: The United States (5), Australia (9) and Japan (10). 18 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Graph 2: Results by year of publication for the "LEZ" term. Source: SCOPUS Finally, for further precision, the search included a variation of the term “small and medium-sized cities”. Added to the previously used terms, it diminished the results to an impractical number, with less than 5 articles in both search engines. In order to increase the relevance of the search and examine other kind of emission reduction measures and the impact on SMSC, the term “LEZ” was substituted by “emission reduction”. In this case, the conclusions found in previous analyses reappeared, along with a very high prevalence of China-based articles (Graph 3). However, after further examination, those Chinese articles were related to natural sciences approach, not focused on urban planning measures. To counterbalance this influence, the phrase “NOT China” was added, which showed results that were roughly identical to those found under the search for “LEZ”. Overall, three main conclusion can be taken from this bibliometric analysis on the literature of LEZ/emission reduction measures on small and medium-sized cities. Firstly, it is not a widely researched topic, all the advanced searches that were conducted only resulted in a maximum of 200 useful articles, with very specific searches even showing a single or zero results. Secondly, the relevance of the topic is very recent, starting in the early 2010s, with a stable growth in the following years and a significant increase in the 2022-2024 period (Graph 2). Lastly, the connection between LEZ and any other kind of emission measures and SMSC has not been extensively researched, 19 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO especially in the non-natural sciences department, as no article was found that specifically dealt with this issue. Graph 3: Results by country for the search "small and medium-sized cities AND emission reduction". Source: Web of Science The reasons behind the lack of literature on the topic are long and varied, although some theories could be identified. On the one hand, the existence of Low Emission Zones was negligible until the last decade, reduced to a few European cities. As can be seen in Graph 2, the number of articles is on the rise, which shows the increasing relevance of the topic. On the other hand, many of the articles that have been written until now have focused on capital cities or other major cities. Although this approach leaves out significant parts of the European population, capitals tend to be the most polluted and populated cities in their respective countries. Moreover, they also provide a more extensive access to data for researchers. All in all, it can be established that, albeit not intentionally nor unjustifiably, small and medium-sized cities are being underrepresented in the quest for finding the optimal emission reduction measure. b. LITERATURE REVIEW Previous research on Low Emission Zones is mostly focused on their effectiveness in reducing emissions. There is a wide range of results to be found, each one centred on a specific pollutant, but little is mentioned about the process of establishing LEZ, least of all in a small or medium-sized city. It is within this group of articles that the totality of 20 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO comparative studies between different cities can be found. These studies are conducted within Europe, either within the same country or between big metropolises. One example of this phenomenon is Germany. Because of the country´s early support for Low Emission Zone and the high number of highly populated cities, many comparative studies have been conducted. Morfeld et al. (2014), Cyrys et al. (2013) and Jiang et al. (2016) all analyse the impacts of LEZ in the reduction of air pollution in a number of German cities, and, in the three cases, the research focuses exclusively on measuring emissions. Although different gases and emission are evaluated and the approaches are also diverse, there is no examination on how and why those Low Emission Zones were established. Another way that comparisons between Low Emission Zones have been conducted has been in a continental way. These articles usually offer a bit more of an explanation about when the LEZs were established and which countries were the first one to do so. However, there is really no depth into the steps taken or any other exploration apart from the levels of emissions. In Tögel & Spicka (2014), they analyse how the different restriction categories between Northern states, Sweden, Denmark and the United Kingdom, and Germany, impact the success of a LEZ. Ku et al. (2020) focus their analysis on comparing the Low Emission Zones of Milan, Rome, Paris and London, with especial attention for the basic characteristic (area, type, rules and banned vehicles), as well as the achieved reduction percentage of traffic, No x , PM 10 and CO 2 . Nevertheless, there are some papers that do investigate the effects of Low Emission Zones in topics not related to emissions. However, these analyses are only focused on the results and impacts of LEZs, they do not dwell on the initial and planning phases. Examples of these approaches are Settey et al. (2019) and Dablanc & Montenon (2015) that explore the preparedness of long-distance road carriers to the new measures, such as LEZ, introduced by cities. In other cases, such as Chamberlain et al. (2023) and Broster & Terzano (2025), they study the effects of Low Emission Zones in relation to human health. 21 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO To sum up, a review of the literature on comparative studies of Low Emission Zones highlights the lack of research done on both the initial and planning phases of the project and the under-representation of small and medium-sized cities. Moreover, it is also apparent that most of the research is focused on the impact of LEZ, either through the evaluation of differences in emissions or through other related effects such as health or long-distance transportation. The next sections of this thesis will try to fill the gaps in all of these areas, by exploring the literature on the establishment of LEZ in both small and medium-sized cities as well as in bigger cities. This analysis will be followed by the first comparative examination of the diversity between the initial and planning phases of LEZ of the different sized city groups. 22 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 6. RESEARCH DESIGN Based on the lack of literature on Low Emission Zones and their interactions with small and medium-sized cities, in order to study and answer the research question of this thesis a new method had to be conceived. As previously seen, the previous research is not focused on the managing aspects of LEZs, meaning that there is little theoretical background from which an example can be drawn from. However, the existing literature does provide clues over how and why LEZs were established, principally focused on specific cities. This thesis will follow a qualitative research design. First, a comparative analysis between the two different groups of cities will be conducted. Literature will be studied for understanding the initial and planning phases of establishing a Low Emission Zones and overall conclusions will be extracted from both categories. Next, both sets of inferences will be juxtaposed to expose the main differences between the two. This analysis will produce a baseline that will be used as a reference for assessing national guidelines and case studies, which will be the next and last part of the thesis. For the comparative analysis, the first steps will be directed at identifying the cities that can be used as examples. Because of the lack of literature on the topic, there is not a great variety of cities to analyse. To collect the names of all the European cities that have established a Low Emission Zone, the website CLARS ( Charging, Low Emission Zones, other Access Regulation Schemes) will be used. This website aims to provide information about European cities that have implemented any type of measure that restricts access, including LEZs. Although the page provides information such as the type of vehicle, the requirements for registration or the type of sticker needed, this thesis will only take into account the name of the city. As the website provides the information by countries, the names of all the cities will be gathered state by state and transposed to a spreadsheet. The full list of cities presents some outliers that have to be extracted in order to optimize the search. First of all, some of the cities appear as a part of a metropolitan or provincial area, which have to be deleted. National laws base the obligation of establishing a Low 23 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Emission Zones on the population of municipalities, not on the surrounding areas, thus, this thesis will follow the same approach. Another case is the case of non-city territories, such as the Austrian highways that appear on the list. These will also be excluded as they do not fit the requirements needed for the analysis. Lastly, seasonal Low Emission Zones have to be cut out, as they are only an Italian occurrence, where Winter LEZs are commonplace (CLARS, 2025). The initial list is made up of 431 territorial entities and although those first exclusions reduce the list to 270, a further selection is needed, both for large and for small and medium-sized cities. Small and medium-sized cities represent the majority of municipalities on the list. However, some countries have extended the possibility of establishing Low Emission Zones to smaller towns, meaning that the list needs to be sorted. For a municipality to be considered in the research for small and medium-sized cities it has to meet the description of the OECD, that is, it has to have between 50.000 and 500.000 inhabitants (OECD, 2015). This grouping results in a list of 230 cities (CLARS, 2025). To make the list more functional a further requirement has to be added. A temporal specification was chosen. As previously stated, the research is based on existing literature, thus, the thesis works under the assumption that discriminating against cities that have recently established a LEZ will result in a bigger selection of articles. Cities that had implemented a Low Emission Zone after the 1 st of January 2024 were not taken into account. These criteria significantly reduces the list of qualifying municipalities from 230 to 78, which are distributed by state in the following way: Belgium (1), Denmark (3), France (2), Germany (35), Italy (13), Spain (6), Sweden (7) and the Netherlands (11) (CLARS, 2025). The quantitative elimination process provides a list of 78 cities that may fit the requirements needed for this thesis. However, meeting the criteria is not useful if previous research has not been conducted. As a result, the next step will involve researching academic search engines for articles about the establishment of Low Emission Zones in these cities. Only those with identifiable articles will be kept for 24 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO further examination. In this case, Google Scholar was used as the main search engine, as its ability to search within the text provides broader and deeper results. The terms used for the search were the city name and LEZ, or any variation of the term, as they have been shown to be the most useful. After this analysis, the list is reduced to 19, from which only 7 show articles that explore the establishment and management of LEZ. The rest are either centred on the effects of different pollutants or are just mere mentions in the literature for larger cities (CLARS, 2025). Cities Country Population Implementation date Göteborg Sweden 114.592 01/01/1996 Malmö Sweden 362.133 01/01/1996 Freiburg Germany 236.140 01/01/2013 Uppsala Sweden 245.328 01/01/2013 Castrop-Rauxel Germany 74.370 01/01/2014 Gladbeck Germany 75.799 01/01/2014 Herne Germany 157.368 01/01/2014 Mölndal Sweden 69.364 01/01/2015 Aachen Germany 252.136 01/02/2016 Marburg Germany 77.845 01/04/2016 Umea Sweden 133.093 01/01/2019 Gent (Ghent) Belgium 268.335 01/01/2020 Aalborg Denmark 224.619 01/01/2022 Eindhoven The Netherlands 290.147 01/01/2022 Haarlem The Netherlands 285.886 01/01/2022 Maastricht The Netherlands 122.734 01/01/2022 s'-Hertogenbosch (Den Bosch) The Netherlands 160.740 01/01/2022 Tilburg The Netherlands 227.707 01/01/2022 Utrecht The Netherlands 466.865 01/01/2022 Table 1. Final list of SMSCs that appear in published articles. Source: CLARS/Eurostat For the bigger cities, in order to ensure that the maximum amount of research is taken into account, ten national capitals have been selected. This selection follows a simple threshold: only the ten first national capitals to establish a Low Emission Zone will be taken into consideration. The premise is that national capitals are, most times, the first contact of a state with LEZs and, thus, the most researched. The cities that fit these 25 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO characteristics are: Stockholm, Berlin, Helsinki, Vienna, Paris, Amsterdam, Madrid, Copenhagen, Rome and Brussels. Despite the extensive research conducted on these cities in regard to Low Emission Zones, there is a lack of literature on the more technical aspects of establishing and managing a LEZ. Research on big cities is mainly focused on the effectiveness of the projects, on whether the goals for emission reduction were actually met. As a result, an analysis on the main academic search engines results in fifteen articles that will be included on the research part of the thesis. Some cities, such as Helsinki and Vienna, have not been researched in a way that is relevant for this study, thus, there will not be any further mention of them (CLARS, 2025). Whilst the number of articles may not be big, enough information is provided as to draw significant conclusions, which can be used to improve the implementation of Low Emission Zones in SMSCs. Correspondingly, the next steps will be to individually analyse the articles found for both groups of cities. The goal is to find commonalities within the clusters, identifying them as the main characteristics of both large and small and medium-sized cities. The following step will be to compare the results of both groups and identify the main differences, contrasting the initial and planning phases of the projects. All of this information will be condensed in a table for easy identification and communication. This table will be divided into three columns: one for the distinctive characteristics and the other two for the description of the different approaches taken by the types of cities. Then, taking into account the previously reached conclusions, the Spanish Guidelines for implementing a Low Emission Zone will be examined. Created in 2021, the objective of this guidelines is “ (...) to serve as a guide for those local entities that must design and implement an EPZ.” (Miteco, 2021). Therefore, the goal of this step is to scrutinize this document under the lenses of the comparative analysis conducted in the previous sections. Because the guidelines were written after the implementation of the Low Emission Zone in Madrid, it is assumed that a significant portion is influenced by the experience of the capital. Meaning that there is a high likelihood of finding a bias towards 32 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO The importance of stakeholder support was also researched by Amren and Hedfors in 2023, when they analysed the transport system of the Swedish city of Umea. The local government realized that in order to meet their emission target, both direct and indirect measures were needed. On the one hand, they focused on the pollution emitted by the publicly owned vehicles, the ones they had direct control over. One of the measures introduced was the substitution of the fossil fuel-run local bus fleet for an electric running one. On the other hand, in matters where the government did not have absolute power, in this case, citizens´ decisions, the focus was fixated on green infrastructure investments and on an open communication plan. The city installed charging ports for electric vehicles and encouraged its citizens to choose green mobility alternatives. What Amren and Hedfors argue is that implementing measures own their own is not enough, and that it is on the local governments to define a holistic strategy that actively encourages and fosters citizen participation. Complementary measures The city of Freiburg in Germany has long been regarded as an example of sustainable urban mobility, even before the regional government of Baden-Wurttemberg adopted Low Emission Zones as a priority. The experience of the city offers significant evidence to argue that LEZs, while valuable for emission reduction, are not effective by themselves. Long before 2010, the local government had been following a long-term and comprehensive urban planning strategy, integrating changes in public transport with others in land-use and green spaces (Buehler & Pucher, 2010). Beginning in the 70s, new neighbourhoods had been designed to decrease the presence of vehicles. The strategies followed were varied, such as limiting the availability of parking spaces or the promotion of car-free areas. By the turn of the century, almost 70% of internal trips were made by public transport, cycling of walking (Buehler & Pucher, 2010). Even with higher growing population and employment rates than the national average, the city managed to maintain a green policy (Olaniyi & Ajayi, 2024). 33 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO According to experts, the success of this strategy was largely due to a governance model that considered not only a holistic planning strategy but also encouraged strong citizen participation. Thanks to widespread social and political support, citizens became one with the city´s environmental awareness strategy. This allowed the local government to implement measures that elsewhere would be considered too controversial, such as reducing the number of parking spaces. Moreover, Freiburg was a pioneer in establishing a low-cost monthly public transportation ticket, which attracted 86% of all the previous ticket holders. This promoted a culture of share mobility, which would late reduce major opposition to the establishment of a Low Emission Zone (Olaniyi & Ajayi, 2024). Figure 5. Map of the LEZ in Freiburg. Source: CLARS The establishment of the LEZ in Freiburg was predated by well-established sustainable mobility practices, as is the case of high-quality public transportation, an extensive and well-maintained cycling infrastructure and green urban planning. This illustrates how Low Emission Zones can function as a part of a whole and not as a unique solution to an extensive problem. Without complementary measures, the LEZ in Freiburg would have had a more limited impact, as the population would have lacked a sustainable mobility 34 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO culture. The German city showcases the appropriateness of a large and interdepended framework, where Low Emission Zones are included in a broader strategy (Olaniyi & Ajayi, 2024) (Buehler & Pucher, 2010). Another significant example comes from the mobility plan launched by the Belgian city of Ghent in 2016. That year the city implemented a Low Emission Zone that covered the area within the inner ring road. However, in this case, the municipality did not have a longestablished sustainable culture. Before establishing the LEZ, the local government decided that building such culture was essential. As a result, the LEZ was not implemented as a unique solution to reduce pollution levels, but as a complementary tool of a broader strategy. The local government implemented two additional actions, under the idea that the three measures would work together to enhance each other´s positive effects (Bencekri et al., 2019). The first focused on a transport and mobility policy that both restricted available parking spaces and increased the supply and quality of public transportation. Moreover, the price of parking spaces just outside the Low Emission Zone were increased, so as to discourage short-term parking. The second one was centred on promoting active mobility. The town hall identified streets suitable for pedestrianization and allowed its citizens to design those spaces, converting them into collective gardens or playgrounds (Bencekri et al., 2019). Both of these cases show that Low Emission Zones can and should play a role in achieving emission reduction objectives. Nonetheless, they also demonstrate that effectiveness increases significantly when implemented in a complementary manner with other measures, as seen in the cases of Aachen, Ghent or Freiburg. These last two examples illustrate that the success of such plans depends on building a coherent strategy, one that is aimed towards long-term sustainable mobility. Without this complementariness, governments run the risk of imposing measures that are both unpopular with their citizens and inefficient in achieving their goals (Bencekri et al., 2019) (Buehler & Pucher, 2010). 35 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO The concluding remarks presented by Buehler and Pucher in their 2010 paper summarize this sections perfectly. For them, the design and planning of neighbourhoods had to follow a strategy that ensured both high-density and mixed-use development, so that long car journeys could be discouraged. Moreover, they highlighted a more incentive based approach, where traffic restriction would be followed by affordable and efficient alternatives, which would not be limited to public transportation. Nevertheless, they acknowledged the futility of such a strategy if it is implemented without the approval of the city´s stakeholders. By encouraging sustainability into the city´s identify, such as in Freiburg, cities ensure continuity. Lastly, they also warn about the danger of over relying on a single policy and encourage government to focus on holistic objectives that cover all sustainable aspects. 36 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 8. LEZ IMPLEMENTATION IN LARGE CITIES Pioneers in their countries Low Emission Zones are usually implemented first in the state´s capital city and then expanded to the rest of the country. Because big cities tend to produce the highest national emission rates, governments are more willing to implement fast and effective reduction measures. This was the case of Madrid, where, in 2018, the local government established Spain´s first LEZ. While the main goal was to reduce the concentration of toxic pollutants, the process was also conditioned by need for rapid compliance with the European directive (Lebrusán & Toutouh, 2020). Figure 6. Map of the LEZ in Madrid. Source: Avis The speed at which the project was implemented and the nature of the norm itself led to a tricky political situation after the next local elections, when a new government was elected. The new major downplayed the consequences of climate change and decided not to comply with the Low Emission Zone policy (Lebrusán & Toutouh, 2020). While the measure was subsequently re-introduced, the case of Madrid slowed the implementation of such strategies in the rest of the country. Such was the effect until the central government passed a law that required LEZs in all cities with more than 50.000 37 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO inhabitants, only the Metropolitan Area of Barcelona had followed Madrid´s example (CLARS, 2025). In the case of Germany, Berlin was both the first city to implement a Low Emission Zone and the first to reach the last stage established by the German Guidelines. This meant that the city became the baseline not only for the planning phase but also for the execution period (Aydin & Rauck, 2022). In 2010, Berlin simultaneously implemented stages 2 and 3, two years after establishing the LEZ, based on the need for a faster emission reduction. For other German cities, like Munich and Stuttgart the process was more gradual approach. With the experience of Berlin, the local governments implemented Stage 3 in the span of four and five years, respectively (Fensterer et al., 2014). This pattern is found all over the European continent. Following the establishment of the first and only Zero Emission Zone in Stockholm in 2024, Sweden is examining further implementations in other parts of the country (Bergeling & Watkins, 2024). In Italy, Rome was the first Italy city to implement a congestion charge system, in 2001, which is a form of Low Emission Zone aimed at discouraging vehicle mobility inside certain areas of the historical centre of the city by introducing a fee. In 2008, a similar policy was implemented in Milan and has since been expanded (Ku at al., 2020). Diversity in the design of Low Emission Zones Capital cities are both large in population and extension, which increases the surface area where Low Emission Zones are more effective. In such cases, multiple LEZ are implemented, either through a gradual increase of the zone or by implementing separate zones that cover distinct areas. For example, the city of Paris first established a Low Emission Zone in 2015, banning vehicles that did not meet the established emission criteria from the city´s inner limits at certain hours. Four years later, the Metropolitan government increased the reach of the measure with another LEZ. This new project covered the A86 highway, which surrounds the municipality and parts of its metropolitan area (Poulhès & Proulhac, 2021) (Bernard et al., 2020). 38 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO In Stockholm, the first Low Emission Zone established in 1996 has been followed by another two, the LEZ2 introduced in 2020 and the Zero Emission Zone (ZEZ) that was implemented at the end of 2024. The second LEZ was established in a specific street within the limits of the original LEZ, with the goal of strengthening the restrictions of the first one. On the other hand, the ZEZ prohibits any emission emitting vehicles from entering a specific area of the city, with no exceptions granted. Although these areas were already covered by the initial Low Emission Zone, tightening the rules was considered necessity because the emissions levels varied greatly based on the street (Bergeling, 2024). Figure 7. Map of the LEZs in Stockholm. Source: CLARS Another examples is the city of Rome also established a two-tier Low Emission Zone. Similar to the case of Paris, one covered the historical area in the centre of the city, which has a high business density, and another one that covers the railway ring, which has the highest population density. The reasoning was similar to the previous examples, the local government considered that stricter enforcement was needed (Cesaroni et al., 2011). In Amsterdam, the type of vehicle conditions the Low Emission Zone that can be accessed. Scooter and moped bikes are allowed into a bigger zone than other larger vehicles, such 39 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO as passenger cars, buses and vans (ACL, 2024). Only vehicles that are emission-free are exempt from following these rules (EU Urban Mobility Observatory, 2025). Focus on infrastructure changes and incentives. When implementing a Low Emission Zone in large cities, the second chore of local governments is usually how to provide alternative transportation for the commuting workers and other residents that will no longer be permitted into the area. Because of the dimensions of these cities, transforming them into a walkable city is neither a big priority nor a feasible possibility. Pedestrianization would benefit a small percentage of the population, compared to more extensive reforms (Bergeling, 2024). However, as it will be observed, cities tend to overestimate the influence of their policies, having to amend the new mobility strategies is a usual feature of LEZ implementation in big cities. This can be clearly observed in Berlin. The rules of the LEZ were tightened without consulting the region that surrounds the city, Brandenburg, where a lot of commuters live (Aydin & Rauck, 2022). The local government designed the Low Emission Zone under the assumption that commuters and citizens of the city would unilaterally decide that upgrading their vehicles was more beneficial than facing traffic restrictions, but that was later proven ineffective (Lutz, 2014). It was not until 2018, with the later implementation phases of the LEZ, that the town hall designed a holistic mobility plan. The plan included major improvements in public transport and the construction of pedestrian and cycling friendly public spaces, responding to the mobility behaviours and needs of citizens and commuters alike (Behr, 2024). A similar case happened in Amsterdam. Although the city implemented a Low Emission Zone in 2008, a redesign of the mobility plan was not conducted until 2017 (Kok, 2023). The original plan was to promote the replacement of diesel and petrol vehicles, both heavy and light. The local government considered that by increasingly tightening the characteristics of the vehicles allowed inside the zone, citizens and businesses would be encouraged to change their vehicles (Trip & Konings, 2024). Nevertheless, the city did not consider the implementation of charging stations throughout the city, which would have 40 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO been a more effective way of bolstering the substitution of pollution cars. Even after realizing that a change of strategy was needed, the new policy was still dependent on a changed attitude from citizens. The installation a public charger in any residential street was dependent on the official requests of the neighbours, otherwise the city would not consider them in their plans. (Kok, 2023). Figure 8. Map of the LEZ in Amsterdam. Source: CityLogistics Because Low Emission Zones limit the parking ability of polluting vehicles, some cities have opted for measures that subsidize the transition to green vehicles (EU Urban Mobility Observatory, 2025). Both Amsterdam and Brussels have introduced similar projects in this regard. In the first, both the purchase of electric cars and the scrapping of polluting vehicles is covered. In the latter case, after introducing a LEZ in 2018, and a mobility plan in 2020. In this case, the government promotes the use of public transportation, but, most importantly, offers a bonus for the disposal of a polluting car (Kok, 2023). 41 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 9. COMPARATIVE ANALYSIS Concluding the individual analysis of the characteristics of Low Emission Zone in small and medium-sized cities and large cities, it can be affirmed that clear differences are observed. Although there are many factors that influence the establishment of such projects, four evident characteristics have been identified. Two of these refer to more technical aspects, such as the number and type of zones established, as well as the dimension of decision-taking authority. The latter two focus on aspects of the planning process of a project, which in this case focuses on stakeholder management and the complementary measures that accompany the LEZs. A table will be presented to summarize the findings. When establishing a Low Emission Zone, the willingness and degree of autonomy a municipality receives gains great importance, for a number of reasons. Nevertheless, none is more important than the authority to decide whether or not the city needs a LEZ. For larger cities, that decision usually comes from the local government as a response to the emission levels of the city. After the passing of the European Directive on ambient air quality and cleaner air for Europe (Council of the European Union, 2008), it became apparent that new measures were needed to combat air pollution. National capitals became pioneers in such measures. Because Low Emission Zones are relatively easy to implement and the scenario was so dire, local governments, in cities like Madrid, Berlin or Amsterdam, individually decided that one was needed (Kok, 2023) (Aydin & Rauck, 2022) (Lebrusán & Toutouh, 2020). Because of their early interventions, large cities are allowed significant discretionary power over the strategy to be followed. However, by the time the focus is set on small and medium-sized cities national governments have already taken over. The lessons learned from the national capital and other large cities are gathered and turned into laws and guidelines for the rest of the country. SMSC do not have the authority to decide whether Low Emission Zones are the optimal or even preferential choice to combat high emission levels in their own cities. It is usually the regional or the national government that makes 48 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Furthermore, the document is insistent on local governments‘ independence to implement the Low Emission Zone in the most coherence manner. The sections are full of recommendations, such as what types of parking criteria can be established or the possible sanction criteria. However, while technical aspects can be granted flexibility, as they are the base of any LEZ, other aspects should be more actively encouraged. For example, the impact assessment or the coherence analysis with previous strategies require bigger determination (MITECO, 2021). As it has been proved in previous sections, the implementation of a Low Emission Zone in small and medium-sized cities works best when there is both stakeholder support and it is included in a throughout urban mobility plan. The Spanish Guidelines present these two measures as recommendations; without mention to how important they may be for a successful and effective LEZ (MITECO, 2021). In the case of stakeholders, there are three sections in the implementation process plan where these are mentioned. The first section references communicating with citizens in order to understand their “previous environmental sensitization”, that is to know how receptive they may be to the LEZ. The following mention comes in the form of the socio-economic impact assessment, where the municipalities are encouraged to evaluate the disproportionate effects that the Low Emission Zone may have in different social groups and companies. And the third is found in the last section, which focuses on the sensitization, communication and participation plan, where the Guidelines recommend “(…) the establishment of a consensus mechanism, such as mobility round tables where all the affected stakeholders can have a voice (…)” (MITECO, 2021). From the format in which the recommendations regarding stakeholders are written, with an abundance of verbs such as “encourage”, “recommend” or “promote”, it is apparent that these are not the priority messages that the central government is pushing to the municipalities. Although it is crucial that flexibility is provided to local governments on their preferred strategy to follow, the active participation of 49 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO stakeholders should be embedded in the core of guidelines, from the very beginning and not as the last step of an already long plan (MITECO, 2021). On the other hand, complementary measures do take a large space in the Guidelines, but only in the form of a catalogue. It contains a long list of strategies, from A to J, that local governments can choose from to complement the Low Emission Zone. Despite the significant amount of measure, there is not a single one that proposes sharing the design process with stakeholders. There is no consideration of what the wish of the citizens or other groups may be. Annex I is written with only local governments in mind, both as receptor and as decision-takers, there is no consideration for a co-decision process, where stakeholders can be active participants. For example, Measure A focuses on increasing travel on foot and one of the methods proposed is to “redesign of roads and public spaces” with no mention of including the neighbourhood in the decision (MITECO, 2021). All in all, at first glance, the Spanish Guidelines appear to have included lessons learned from other European countries, such as the flexibility on the form Low Emission Zones can take. Nevertheless, the promotion of the one-size-fits-all approach is still very present throughout the document and there is minimal notice of how LEZ could be differently implemented in certain types of cities. Neither stakeholders’ participation nor inclusive complementary measures are guaranteed or promoted. As it has been shown throughout this thesis, small and medium-sized cities need a more holistic strategy than larger cities, the Spanish government should have analysed this phenomenon and ensure that the official Guidelines took into account all the realities of the country (MITECO, 2021). 50 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 11. CASE STUDY: BASQUE CITIES In this section an analysis of planning phase of the three Low Emission Zones in the Basque Country will be conducted. This region has been chosen because its three provincial capitals are examples of the different types of cities that can be found within the small and medium-sized city cohort. Bilbao is the biggest city in the Basque Country, although it is still considered a medium-sized city, with 348.089 inhabitants. Next is Vitoria-Gasteiz with 255.423 inhabitants, falling into the same category, and last, Donostia-San Sebastián, the only small city in this list with 188.136 inhabitants (INE, 2024). Examining the differences between the conclusions extracted from previous sections and the strategies followed by these three diverse cities will showcase a real-life example of how LEZ are implemented and how the Spanish Guidelines are adopted. Before proceeding, brief notes have to be made. First, it must be noted that not all three cities have followed the same timeline. Bilbao was the first city to implement a Low Emission Zone in the Basque Country, which was enacted on the 15th of June 2024. Moreover, it is the biggest city in the region, with a metropolitan area of around 1 million inhabitants. These dynamics may have affected the implementation process of the LEZ, as it was the first one and also the one that had to adjust for the higher number of people. The LEZ in Donostia was introduced in January 2025, whilst the one in Vitoria-Gasteiz is planned for the 15th of September 2025. In these two cases the size and approaches should be similar (CLARS, 2025). On the other hand, it must also be taken into that these municipalities are the capital cities of their provinces, with the consequences this may have had in terms of resources and prioritization. Lastly, it must also be mentioned that despite the three cities being part of the same autonomous community, the Basque Country, the regional government lacks the competences to influence in the implementation of Low Emission Zones, this means that all three followed the Spanish law and guidelines. 51 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO a. CASE STUDY I: BILBAO As with the rest of the cities, the local government of Bilbao produced a memory document where it described all the actions taken for the implementation of the Low Emission Zones, as well as the technical details. One of these sections, focuses on the coherence of the new project with the previous strategies that the city had already implemented, such as, the Sustainable Urban Mobility Plan 2015-2030 or the region´s Strategic Plan for Public Transportation 2018-2028. The analysis conducted is superficial, focused only on acknowledging the plans that the LEZ should fit into (Ayuntamiento de Bilbao, 2024). Furthermore, Bilbao´s plan also includes a section for analysing the social, genre and disability impact the Low Emission Zone will have. The goal was for the new project to take into account how differently it would impact the different realities found in the city. It was centred in six parameters: road safety, sustainability, socioeconomics, gender and social inclusion, accessibility, and health. The result was the inclusion of more measures focused on pedestrianization, which the study found disproportionately affect women more, and on ensuring both physical and technological accessibility for vulnerable groups (Ayuntamiento de Bilbao, 2024). The local government´s document also covers a communication and sensitization plan, whose goal is to promote and make the public aware of the Low Emission Zone and its consequences. Although the most interesting part of this section is the second subsection, focused on citizen participation. The town hall organized a number of workshops with the main affected stakeholders. This process had three objectives: gather data and arguments to analyse and justify the LEZ, strengthen the sensibility and communication plan, and ensure transparency in the process. The city wanted to ensure that the stakeholders felt listen to and ensure that they could establish the Low Emission Zone with minimal disruption to everyday life. Nevertheless, there is no mention on how these discussions influenced the design of the project (Ayuntamiento de Bilbao, 2024). 52 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO b. CASE STUDY II: DONOSTIA In the case of Donostia-San Sebastián, the document is more extensive but follows the same structure as the one created by the town hall of Bilbao. The difference appears in the extension of the technical aspects of the Low Emission Zone, but the rest of the content is extremely similar. On the one hand, it contains a section where the coherence of the plan for the Low Emission Zone with the rest of previously established strategies is examined. In the case of the Donostia, the analysis involved a bigger number of plans than in the case of Bilbao, as strategies such as the Action Plan on Noise Pollution or the Municipal Study of Mobility to the Center are also included. The analysis explores in greater detail the relationship between the LEZ plan and the rest of them, but with no mention to the adaptations needed (Ayuntamiento de Donostia-San Sebastián, 2025). On the other hand, a section for the social, genre and disability impact was also conducted. In the first case, the town hall established that no added measure was needed as there was no special inference for the inhabitants of the city. The genre impact analysis did find differences in the behaviour pattern of both genres, but the document does not include any additional measure that will solve those differences. There is only a mention of how the implementation of a Low Emission Zone will improve women´s health. Lastly, the analysis of the impact for the more vulnerable collectives showed that there was no need for any auxiliary measures (Ayuntamiento de Donostia-San Sebastián, 2025). Lastly, although the document is, in general, far more extensive than Bilbao´s, the section which centres on citizen participation is significantly smaller than its counterparts, covering barely a page and a half. The town hall identified three mechanism of citizen participation: representative, through the elected officials; conversational, between politicians, municipal technicians, and citizens; and, direct democracy, through popular consultations. It mentions that stakeholder participation is to be conducted through spaces for formation, information, and constructive dialogue, but no further information is provided. Furthermore, it 53 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO highlights, that the consultations will be non-binding but with the possibility of having an impact on the project (Ayuntamiento de Donostia-San Sebastián, 2025). c. CASE STUDY III: VITORIAGASTEIZ Although the Low Emission Zone in the city of Vitoria-Gasteiz is not yet operative, the town hall published its memory document in July 2024. As in the rest of the cities, the document follows the structure recommended by the Spanish Guidelines, even though the length is more similar to San Sebastian´s than to Bilbao´s. The coherence section contains an even broader analysis than the other two cities. Not only does it include the local and provincial strategies, but it also takes into account plans created by the Autonomous Community, such as the Urban Agenda of the Basque Country “Bultzatu 2050” or the Basque Energy Policy to 2030. Although, similar to Bilbao, the analysis is not extensive and is summarized in a table format (Ayuntamiento de Vitoria-Gasteiz, 2025). The local government also included the section about the social, genre and disability impact. This part of the document is short and is mostly centred on the advantages of the Low Emission Zone on the life of these communities. It does acknowledge that transportation patterns for females are more complex, and, thus, that improvements in the public transportation systems and urban planning will be beneficial for the group, without explaining what they will look like. The same argument is used for the more vulnerable collectives. Although, in relation with limited mobility citizens, there is mention for authorizing special mobility measures within the LEZ (Ayuntamiento de Vitoria-Gasteiz, 2025). The last section, the one focused on the sensitization and communication campaign follows the same structure as the previous two cities. A communication campaign was established with the goal of spreading information about the Low Emission Zone and a participative process was initiated. The process was initiated with a presentation of the project followed by a question round for those that signed up. 54 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Then, two meetings were organized, where citizens could share their ideas and contributions. The last paragraph mentions the possibility of establishing a “contrast group” that would be formed from the participants of the meetings. The objective would be for the group to become a reference for citizens during the whole process of establishing the LEZ. However, it is mentioned that the group will only be formed if enough interest is detected, and as in the previous cases, no explanation is given as to the influence these meetings may have in the design (Ayuntamiento de Vitoria-Gasteiz, 2025). d. CONCLUSIONS An analysis on the planning documentation for the establishment of the Low Emission Zone in all three Basque capitals shows a clear influence of the Spanish Guidelines. The format is the one recommended by the central document and the content also reflects certain technical directions. One clear example is that all three have a specific section that examines the coherence of the LEZ plan with previously implemented plans, such as air quality or noise reduction plans. However, there is a clear difference between the level of detail analysed by the three cities, whereas San Sebastián is the most specific, Vitoria takes into account a wider range of plans, implemented at different administrative levels. This fact showcases the flexibility given to cities to adapt the recommendations to the needs of the city, as well as the unwillingness of these local governments to extensively explore the coherence of the new plan. While multiple plans are mentioned, no local government explores what changes are needed to adapt the LEZ to their findings. The second section that has been identified was centred on the impact of the Low Emission Zone on the everyday lives of the citizens, and especially the most vulnerable communities, such as women and disabled people. All three cities conducted a study on how the new plan would affect their population, but only Bilbao seemed to reflect on the identified issues and proposed solutions. Although it did not present broad changes, it is a significant improvement from the approach taken by the other two cities. For the local governments of Donostia and Vitoria only 55 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO used arguments for how the LEZ would improve the lives of these communities, without identifying potential adaptions that may be included in the plan. Related to this lack of open perspective is the last section that has been analysis: the communication and sensitization plans. All three documents reflect the same level of citizens participation: passive. The majority of the sections are focused on the communication plan, whose sole purpose is to make sure all the citizens are aware that a Low Emission Zone is going to be established in the city. The part for citizens participation is significantly smaller and non-binding. All three cities have included participatory processes, first with stakeholders to understand the impact on the different collectives, and then, with the public to listen to their questions and suggestions. Although the documents were written after these processes were organized, there is no mention of a single citizen proposal that was accepted and introduced into the planning process. It seems that this last section was just used to complete the list provided by the Spanish Guidelines, without any willingness from the local government to include its citizens and associations as active participants of a project that would affect the everyday life of a lot of people. All in all, after an in-depth lecture of the three documents, it can be said that all three cities have implemented the one-size-fits-all approach encouraged by the Spanish Guidelines. Meaning that the recommendations provide by the Spanish government for cities to adapt the Low Emission Zones to their particular needs have not been followed. The planning has relied solely on the local governments, with minimal input from stakeholders, as there is no mention of inclusion of any citizen-led suggestion. No city fulfils the successful characteristics identified in the ninth section of this document for small and medium-sized cities. Because of these, it must be affirmed that the afore-identified characteristics of small and medium-sized cities are not fulfilled by the three Basque cities, indistinctly of the size. 56 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 12. DISCUSSION AND RESULTS The goal of this section is to put together all the findings of the research, encompassing the case studies, the legal framework, and the comparative analysis of the different Low Emission Zones in small and medium-sized cities. To achieve this objective, the section will begin with a comparative table that gathers the relevant population and area data of the three Basque capitals. This approach allows for an easier understanding of the territorial and demographic dimension of the LEZ. The table will be useful as a base for the other two subsections of the section. In the first, a good practice guide will be presented, created based on the Low Emission Zones analysed throughout this whole thesis. On the second subsection, the opposite will be conducted, centred on the areas that have been identified as weaknesses. The combination of both approaches will lead not only to an evaluation of the policies, but also to proposing potential improvements. a. QUANTITATIVE COMPARISON OF POPULATION AND AREA One of the most relevant aspects to understand the actual impact of a Low Emission Zone is its territorial and demographic dimension. That is, to perceive how much of the public space and how many people are directly affected by the introduction of such measure. Moreover, this comparison gains significant relevance when talking about small and medium-sized cities, where the choice made when defining the perimeter of the LEZ can substantially affect its support, effectiveness, and adaptability. The following table shows the data for Bilbao, Donostia-San Sebastián, VitoriaGasteiz. The information included corresponds to the population and territorial area in absolute and relative terms in terms of the Low Emission Zone. Furthermore, the percentage of citizens and area affected will also be calculated. It must be noted that other cities were researched, but they were not included because of a lack of data 57 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO Total population Affected population % affected population Total area (km2) Affected area (km2) % affected area Vitoria-Gasteiz 238.247 19.438 8,16 % 277 0,82 0,29% Bilbao 353.187 51.086 14,46 % 41 2,14 5,22% Donostia-San Sebastián 185.506 22.468 12,11 % 61 1,2 1,97% Table 4. Population and area affected by the LEZ in Bilbao, Donostia-San Sebastián and Vitoria-Gasteiz. Source: ING Figure 11. Delimitation of the LEZ in Donostia-San Sebastián. Source: Ayuntamiento de San Sebastián Figure 9. Delimitation of the LEZ in Bilbao. Source: Ayuntamiento de Bilbao Figure 10. Delimitation of the LEZ in Vitoria-Gasteiz. Source: Ayuntamiento de Vitoria 64 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO designed nor implemented. In Bilbao, on the other hand, there is a greater connection between the diagnosis and the design, as the city turns to greater pedestrianization and technological accessibility. Nevertheless, there is still a significant gap to guarantee that equity is more than a check on a list (Ayuntamiento de Vitoria-Gasteiz, 2025). 3. Coherence with other strategies As in the previous case, another aspect that is included in the documentation but is not sufficiently developed is the integration of the Low Emission Zone with the already existing strategic plans, both local and regional. Even though the plans of the three city analyse previously implemented mobility, sustainability, air quality and urban regeneration plan, the coherence process is just a formal declaration, without analysing how to integrate all of them in a holistic approach, nor identifying the conflicts and complementarities between them. Such is the case of Bilbao, where there a mention to the 2015-2030 Sustainable Mobility Plan, but there is no in-depth analysis of how the Low Emission Zone will transform, improve, or update that plan. It is not enough with ensuring that the LEZ will be in tune with previous strategies, it is also crucial to show how they all will be integrated in a shared and intersectional way (Ayuntamiento de Bilbao, 2024). 4. More accessible communication The communication from the local governments of the three capitals has been mostly focused on noticing citizens of the technical aspects of the Low Emission Zones, such as dates and norms. There has not been any effort to develop a marketing strategy that connects with citizens and allows them to form an attachment with the project. Moreover, at times, the communication has been seen as difficult or excessively technical, which has hindered the understanding and social support of citizens. The local government of Vitoria-Gasteiz, for example, introduced some informative actions, but with limited formats. The three capitals have a lot of margin to develop 65 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO more pedagogical sensibilization campaigns, which include clear language and visual examples, with present both in traditional and social media formats. The messaging should be centred on more familiar topics, such as, clearer air, health, and more sustainable and safer mobility (Ayuntamiento de Vitoria-Gasteiz, 2025). 5. More visible and progressive complementary measures As it has been established throughout this whole thesis, Low Emission Zones are less effective when they are implemented in isolation. They must be joined by complementary measures that strengthen the impact and ease the transition towards a more sustainable mobility. In none of the three capitals´ documentation is it clear that such actions are to be taken. Not even low cost but highly impacting measures, such as pedestrianization, more cycling lanes or alternative parking options. In Donostia-San Sebastián, for example, the technical design is sound, but the local government does not consider an urban transformation that works hand in hand with the LEZ. In small and medium-sized cities, these improvements, which in some cases are minor ones, can make a huge difference both in public perception and in the actual effectiveness of the project (Ayuntamiento de Donostia-San Sebastián, 2025). 6. Lack of monitoring and accountability There is a clear lack of monitoring mechanisms, which would follow the implementation process and the achievement of the objectives of the project, as well as enacting corrective actions. Even though some cities mention the need to follow up on the implementation process, no specific indicators are established, nor is there a plan for periodic check-ins. There is no mention for such measure in the eighty pages of documentations produced by the local government of Bilbao, nor in the rest of the cities. No mention to how the effects of the Low Emission Zone will be evaluated, nor how the citizens will be informed of the progress or necessary updates. Small and medium-sized 66 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO cities can easily correct this shortage by creating a simple and interactive dashboard, that citizens can easily access to check on the evolution of the project. This kind of initiative would ensure an easier adaptation of the measures and an increase in citizens trust. d. DISCUSSION A comparative analysis is always a challenge and in the case of Low Emission Zones that challenges is exponentially bigger. The popularity of the measure is new and already diminishing, as it can be seen in France and Germany where some have already been eliminated (Taus, 2025) (Baden-Württemberg, 2025). As a result, studying the effects of LEZ become increasingly vital, either to argue for its elimination or for its strengthening. This thesis has tried to fill a major gap in the already small literature by showing that comparative analyses about the planning of LEZ in small and medium-sized cities can be conducted. The results show that the process is not as easy as it may look in European directives or national guidelines, especially for smaller cities. A holistic approach is needed, where the focus is shared between different measures and stakeholders are invited to actively participate. Both strengths and weaknesses have been identified, with a special emphasis in the three Basque capitals. Compared to the cases examined in earlier sections, where the Low Emission Zone implementation took a more inclusive approach, these cities have been locked in a one-sizes-fits-all plan. While the results are still unavailable, the literature suggests that they may be in need of modifications. Nevertheless, such scenario is not novel, if the three governments decide to abandon their standardized plan, they will realize that they have plenty of examples to learn from. In the Basque Country, three other cities can be forced to implement a Low Emission Zone: Barakaldo, Getxo and Irun. The Barakaldo and Irun have already started developing the design for the LEZ, while Getxo´s future is still uncertain. Based on the lessons learned and the weaknesses detected in previous chapters, this thesis 67 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO would point the local governments in two directions. On the one hand, it would recommend a big implication of stakeholders, by listening to their ideas and working together to ensure that both their needs and those of the city in general are fulfilled. On the other hand, it would encourage the town halls to only use the Spanish Guidelines as a baseline and to build on top of them. The goal would be to adapt the recommendations to the different realities of the city, going further than the one-size-fits-all approach presented in them. All in all, this thesis wants to promote a more holistic approach to the initial and planning phases of the Low Emission Zone, so that the project is built around the city and not the city around the project. 68 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO 13. CONCLUSIONS This thesis has tried to find an answer to the suitability of Low Emission Zones to adapt to the needs of small and medium-sized cities, and the search has expanded from literature reviews to comparative analysis to researching three case studies. The main conclusion is that although the main characteristic of a successful Low Emission Zone for SMSC can be easily identified, in practice, these procedures have not been well executed. Neither in the recommendations provided by national governments, nor by the local governments when designing the implementation of the LEZ. As it can be seen in Section 7 (LEZ Implementation in SMSC), for a Low Emission Zone to be effective when established in a small or in a medium-sized city, three characteristics are essential: the strategy has to be personalized for the necessities of the city, stakeholders should be active and supportive participants in the process, and, lastly, complementary measures that work together with the LEZ are essential. Section 10 (Spanish Guidelines) and 11 (Case Studies: Basque Cities) show the lack of internationalization of how these qualities, and, thus, were not reflected in the design of the Spanish Guidelines or the planning of the Low Emission Zones in Bilbao, Donostia, and Vitoria-Gasteiz. The results show how even though literature backs the theory of personalized solutions, states and cities prefer a one-size-fits-all approach. The reasons may vary, but it is clearly easier to establish a single model and adapt to each city, without taking into considerations the particularities of it. Moreover, it is not only that the plans are not adapted to the city, but, as it has been proven, citizens are also not encouraged to participate. At least not in an active manner, nor following the model of small and medium-sized cities, which has proven successful in other cities such as Ghent or Freiburg. Lastly, the complementary measures and the coherence with other plans, both established in the Spanish Guidelines, are given minimal importance. 69 BILBOKO INGENIARITZA ESKOLA ESCUELA DE INGENIERÍA DE BILBAO There is no telling the consequences of the attitudes taken by the Basque cities, since the implementation phase is too recent. However, previous experience, like the case of Amsterdam, shows that there may be a time when a more holistic approach is needed in order to implement further measures that lower emissions (Kok, 2023). Public support for such measures may also constitute an issue in the near future. A recent study by Gizater for the Basque Broadcasting group shows that only 39,9% of young people are in favour of more limitations (Gizaker, 2025). On the other side of the border, France has eliminated all Low Emission Zones, on the basis that it affected mostly low-income citizens (Taus, 2025). With this, it becomes apparent that without public support LEZs are doomed to failure. . Nevertheless, it must not be forgotten that one of the goals of this thesis was to fill the large gap that exists on the literature of Low Emission Zones. While that goal may be fulfilled, that same lack of literature may diminish the validity of this research. Not a lot has been studied from a social or comparative perspective, thus, the conclusions here presented may be skewed. Moreover, because the data is limited to Europe, the image presented may be short-sighted. This thesis has investigated and analysed from the literature available at the moment, which does not mean that the conclusions reached are factually correct. Thus, it is of the utmost importance that further research is conducted. Not only because of climate change, but also because cities have to be liveable and accessible for its population. Future articles and thesis should not limit their reach to emissions but should explore socio-economic impacts of Low Emission Zones and other emission reducing measures. It is also important for the research to focus on SMSC, especially on comparative analysis between different smaller cities of a number of countries. 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