Evaluation of the Implementation of a Low Emission Zone in Lisbon


The city of Lisbon, like many others in the EU region, introduced a Low Emission Zone (LEZ) as a tool for improving air quality in its city centre. This kind of emission reduction schemes is always controversial since it might lead to significant changes in the daily behaviours of its inhabitants. In order to evaluate the effects of the measure, an estimation of the impact of the introduction of the Lisbon LEZ was performed. Real traffic counting and fleet characterization combined with CORINAR-based emission inventory methodology allowed to estimate the impacts of three different scenarios applied to the “business as usual” condition (current vehicle fleet) ranging from “no circulation from non- compliant vehicles” to an “aggressive fleet renewal”. Results highlight the high percentage of atmospheric emissions of PM10 and NOx that might result from certain fleets like taxis and buses, especially because there was an emphasis in standardized/normalized estimations (emissions per 1000 vehicles) in order to allow different strategic approaches. The total reduction of PM10 emissions associated to each scenario vary between 6 ton.year-1 (scenario 2) and 8 ton.year-1 (scenario 1), or 25% and 34% less emissions. In terms of NOxemission reductions vary between 6 ton.year-1 (scenario 2) and 57 ton.year-1 (scenario 1), or 1% and 7% less emissions. The Lisbon LEZ is therefore much more efficient in reducing PM10 emissions compared to NOx. Major reduction in PM10 and NOx emissions are to be expected with a moderate intervention in the (relatively old) taxi fleet in Lisbon while for passenger cars the impact is limited. However in absolute terms and due to its urban mileage passenger cars should also continue being included in Lisbon LEZ. Simultaneously, an effort in the increase of dedicated lanes for public transport should be made, for further reductions in PM10 and NOx emissions.

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Ferreira, F. , Gomes, P. , Carvalho, A. , Tente, H. , Monjardino, J. , Brás, H. and Pereira, P. (2012) Evaluation of the Implementation of a Low Emission Zone in Lisbon. Journal of Environmental Protection, 3, 1188-1205. doi: 10.4236/jep.2012.329137.

1. Introduction

The highest probability of employment, higher variety of medical care, educational services and multiple cultural programs, associated to a higher education level are pushing countries populations to their cities. During the last 50 years it may be observed that Portugal is increasing its urban population at an average rate of 5% per decade; after the middle 80’s of the last century this rate is slightly higher, around 6 %. However, it was only in 2010 that Portugal reached the same percentage of urban population as Europe in 1960 (Figure 1, [1]).

Since 75% of the European population lives in urban areas, it causes stress and pressures to the urban environment, population health and quality of life (in general) and, ultimately, in their economic performance but also in their nearby rural sites [2,3]. Having these, and related issues in mind, a Thematic Strategy on the Urban Environment has been published by the European Commission [4] with the objective of contributing to “a better quality of life through an integrated approach concentrating on urban areas” and “to a high level of quality of life and social well-being for citizens by providing an environment where the level of pollution does not give rise to harmful effects on human health and the environment and by encouraging sustainable urban development”.

Within this Thematic Strategy, four main crosscutting aspects were considered, namely: sustainable urban transport, sustainable urban management, sustainable urban construction, and sustainable urban design. On its side, the Thematic Strategy on air pollution [5] in its aim to reduce air pollution concentration to “levels of air quality that do not give rise to significant negative impacts on,

Figure 1. Urban population in Portugal (PT) and Europe between 1950 and 2010.

and risks to human health and the environment”, articulates its objectives with the other policy areas, as Energy, Transport, Agriculture, among others. Hence it is almost natural that searching for solutions on promoting better quality of life in cities, urban transport management in cities may be regarded as key target to focus on, since traffic is one of the major air pollutants emitters, includeing greenhouse gases, besides being a relevant noise producer [3]. These singularities led to several approaches in Europe and one of them was the adoption of the Action Plan of Mobility [6].

Restringing the access to vehicle in the cities may be, in principle, a valuable way to reduce noise and ambient concentrations of atmospheric chemical species. Due to the profusion of access restriction solutions among Europe there are studies that try to collect, summarise, analyse and give recommendations on this kind of solutions [7].

According to [8], assessment restrictions are classified into: 1) point based; 2) cordon based, 3) area license based pricing; 4) distance/time based.

1.1. Low Emission Zones

A Low Emission Zone (LEZ) is a defined area that can only be entered by vehicles meeting certain emissions criteria. A LEZ can lead to major air quality improvements because it capitalises on recent EU legislation for road vehicles, which have set progressively tighter emission limits on new vehicles manufactured over the past decade [8]. LEZ schemes can take many forms based on the geographical area they cover, the times at which the LEZ is in force, the vehicle emissions standards required for vehicles to enter the zone, the types of vehicles that need to comply with the LEZ, and the implementation and enforcement approaches used [8,9].

Due to its flexibility on rules to be applied (type of vehicle and restriction time of day) and inherent easiness on application and understanding it became one of the most popular measure adopted by several municipalities, especially those with more than 200,000 inhabitants [7].

In Asia, LEZ are also implemented in Tokyo [10] and tested in Beijing [11]. However, the broader application area license based pricing are more common and is also observed in the United States. What may be the oldest one was defined in Singapore, operating since 1975 [11, 12].

Over Europe, information on restriction areas on European cities particularly on LEZ is gathered in a web site, supported by the European Union [13]. The LEZ site has presently registered 323 cities where LEZ have, or are planning to be, implemented. Since the inner part of some Italian zones have LEZ (like Lombardy), in reality this figure is even greater.

With the LEZ implementation in an area of a city several objectives may be met simultaneously. Limiting vehicles circulation on a city area imposes subsequent reductions on emissions of air contaminants, greenhouse gases and noise, with positive impacts on population health, along with eventual compliance on climate change and energy policy commitments.

However, and as stated in the European LEZ site [13], the legal air quality standard compliance for human health protection is the major implementation driver of this type of emission reduction schemes across Europe, namely in London [14]. It is also the case of the city of Lisbon, Portugal.

1.2. Air Quality Levels in Lisbon

Lisbon environmental regional authority has identified exceedances to legal limit values (LV) plus margin of tolerance, set in the Directive 2008/50/EC on ambient air quality [15], in agglomerations in its area of jurisdiction, since 2001, as is the case of Northern Metropolitan Lisbon Area (AMLN).

The European Commission has had to start infringement proceedings against 10 Member States, including Portugal, for failing to comply with the EU’s air quality standard for dangerous airborne particles known as PM10 [16]. Currently there are 19 infringement cases pending against Member States which failed to comply with the air quality limit values for particulate matter and/or sulphur dioxide set out in [15]. Also, the Commission is currently assessing Member States’ notifications requesting extensions of the deadline to comply with the limit values for nitrogen dioxide (until 2015 at the latest). The Commission can also open an infringement case against a Member State that did request a time extension but for which this request was rejected [17].

Figure 2 shows the evolution of NO2 and PM10 levels and legal compliance relating to each limit value (annual

Conflicts of Interest

The authors declare no conflicts of interest.


[1] The World Bank, “Urban Population (% of Total),” 2012. http://data.worldbank.org/indicator/IS.VEH.ROAD.K1/countries/1W-PT-EU?display=graph
[2] European Environmental Agency, “Ensuring Quality of Life in Europe’s Cities and Towns. Tackling the Environmental Challenges Driven by European and Global Change,” EEA Report, 2009.
[3] European Environmental Agency, “The European Environment State and Outlook 2010—Urban Environment,” 2010.
[4] European Commission, “Communication from the Commission to the Council and the European Parliament on Thematic Strategy on the Urban Environment,” 2006.
[5] European Commission, “Thematic Strategy on Air Pollution,” 2005.
[6] European Commission, “Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee of the Regions—Action Plan on Urban Mobility,” 2009.
[7] Tender No. TREN/A4/103-2/2009, “Study on Urban Access Restrictions,” 2010. http://ec.europa.eu/transport/urban/studies/doc/2010_12_ars_final_report.pdf
[8] M. Browne, J. Allen and S. Anderson, “Low Emission Zones: The Likely Effects on the Freight Transport Sector,” International Journal of Logistics Research and Applications: A Leading Journal of Supply Chain Management, Vol. 8, No. 4, 2004, pp. 269-281.
[9] National Society for Clean Air (NSCA), “Low Emission Zones 2003 NSCA Special Report,” 2003.
[10] H. Wolff and L. Perry, “Keep Your Clunker in the Suburb: Low Emission Zone and Adoption of Green Vehicles,” 2012. http://faculty.washington.edu/hgwolff/LEZ.pdf
[11] F. Costabileand and I. Allegrini, “A New Approach to Link Transport Emissions and Air Quality: An Intelligent Transport System Based on the Control of Traffic Air Pollution,” Environmental Modelling& Software, Vol. 23, No. 3, 2008, pp. 258-267 doi:/10.1016/j.envsoft.2007.03.001
[12] M. Li, “Estimating Congestion Toll by Using Traffic Count Data—Singapore’s Area Licensing Scheme”, Trans- portation Research Part E, Vol. 35, No. 1, 1999, pp. 1- 10.
[13] Low Emission Zones in Europe, 2012.http://www.lowemissionzones.eu
[14] F. Kelly, B. Armstrong, R. Atkinson, H. R. Anderson, B. Barratt, S. Beevers, D. Cook, D. Green, D. Derwent, I. Mudway and P. Wilkinson, “The London Low Emission Zone Baseline Study. Investigator’s Report, in the London Low Emission Zone Baseline Study with a Critique by the HEI Health Review Committee,” Research Report 163, Health Effects Institute, Boston, 2011.
[15] 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.
[16] “Air Pollution: Commission Starts Legal Action against 10 Member States over Airborne Particles,” 2009. http://europa.eu/rapid/pressReleasesAction.do?reference=IP/09/174
[17] “Parliamentary Questions: Answer Given by MrPoto?nik on Behalf of the Commission,” 2012. http://www.europarl.europa.eu/sides/getAllAnswers.do?reference=E-2011-011869&language=DA
[18] Portaria n. 715/2008, Diário da República, 2.a Série, N. 151, 6 de Agosto de 2008, pp. 34959-34968.
[19] Despacho n. 20763/2009, Diário da República, 2.a Série, N. 180, 16 de Setembro de 2009, pp. 37809-37866.
[20] “Zona de Emiss?es Reduzidas. Cidade de Lisboa,” 2002. http://www.cm-lisboa.pt/archive/doc/ZER-seg_fase_MapaZER_2aFase.pdf
[21] V. Góis, H. Maciel, P. Torres, S. Mesquita, F. Ferreira, C. Almeidaand and L. Nogueira, “A Detailed Urban Road Traffic Emissions Inventory Model Using Aerial Photography and GPS Survey,” 16th Annual International Emission Inventory Conference—Emission Inventories: Integration, Analysis, and Communications, Raleigh, 2007. http://www.epa.gov/ttn/chief/conference/ei16/session9/gois.pdf
[22] “EMEP/EEA Air Pollutant Emission Inventory Guidebook—2009. Parte B: Sectorial Guidance Chapters, Energy, Combustion, Road Transport,” European Environment Agency, 2010. http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1.a.3.b-road-transport-gb2009-update.pdf
[23] H. Brás, “Avalia??o dos Benefícios da Implementa??o de Zonas de Emiss?es Reduzidas em Lisboa,” Master Thesis, Universidade Nova de Lisboa, Lisboa, 2012.
[24] P. Torres, “Velocidade méDia de Circula??o de veículos Ligeiros na Cidade de LISBOA. 28 de Fevereiro de 2012,” Comunica??oescrita (Average Speed of Circulation for Passenger Cars in Lisbon. Personal Communication).
[25] “EMEP/EEA Emission Inventory Guidebook 2009, Parte B: Sectorial Guidance Chapters, Energy, Combustion, Road Transport,” European Environment Agency, 2012. http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1.a.3.b-road-transport-gb2009-update.pdf
[26] “EMEP/EEA Emission Inventory Guidebook 2009, Parte B: Sectorial Guidance Chapters, Energy, Combustion, Road Transport,” Annex Files for Heavy Duty Vehicles Emission Estimation, European Environment Agency, 2009. http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1.a.3.b-road-transport-annex-hdv-files.zip
[27] R. Hagman, K. I. Gjerstad and A. H. Amundsen, “NO2 Emission from the Fleet of Vehicles in Major Norwegian Cities—Challenges and Possibilities towards 2025,” 2011.

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