Air pollution impacts of speed limitation measures in large cities: The need for improving traffic data in a metropolitan area José M. Baldasano a, b, * , María Gonçalves b , Albert Soret b , Pedro Jiménez-Guerrero b,1 a Environmental Modelling Laboratory, Technical University of Catalonia, Avda. Diagonal 647, Edificio H, Oficina 10.23, 08028 Barcelona, Spain b Barcelona Supercomputing Center e Centro Nacional de Supercomputación (BSCeCNS), Earth Sciences Department, Jordi Girona 29, Edificio Nexus II, 08034 Barcelona, Spain article info Article history: Received 12 March 2010 Received in revised form 6 May 2010 Accepted 7 May 2010 Keywords: Urban air quality Air quality modelling Traffic emissions Atmospheric management Barcelona Metropolitan Area abstract Assessing the effects of air quality management strategies in urban areas is a major concern worldwide because of the large impacts on health caused by the exposure to air pollution. In this sense, this work analyses the changes in urban air quality due to the introduction of a maximum speed limit to 80 km h 1 on motorways in a large city by using a novel methodology combining traffic assimilation data and modelling systems implemented in a supercomputing facility. Albeit the methodology has been non- specifically developed and can be extrapolated to any large city or megacity, the case study of Barcelona is presented here. Hourly simulations take into account the entire year 2008 (when the 80 km h 1 limit has been introduced) vs. the traffic conditions for the year 2007. The data has been assimilated in an emission model, which considers hourly variable speeds and hourly traffic intensity in the affected area, taken from long-term measurement campaigns for the aforementioned years; it also permits to take into account the traffic congestion effect. Overall, the emissions are reduced up to 4%; however the local effects of this reduction achieve an important impact for the adjacent area to the roadways, reaching 11%. In this sense, the speed limitation effects assessed represent enhancements in air quality levels (5e7%) of primary pollutants over the area, directly improving the welfare of 1.35 million inhabitants (over 41% of the population of the Metropolitan Area) and affecting 3.29 million dwellers who are potentially benefited from this strategy for air quality management (reducing 0.6% the mortality rates in the area). Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Improving air quality in urban areas is nowadays an important environmental challenge (Akimoto, 2003; Molina and Molina, 2004). In addition, worldwide epidemiological studies show a consistent increase in cardiac and respiratory morbidity and mortality from exposure to air pollution (Dockery et al., 1993; Nel, 2005; Pope and Dockery, 2006). As well as a source of local pollu- tion, urban activities contribute to transboundary pollution and the increase of greenhouse gases (GHGs) concentration (Fenger, 1999; Baldasano et al., 2003). The public administrations are testing management strategies mainly addressed to reduce on-road traffic emissions, because this sector is the largest contributor to anthropogenic pollutants emissions in the urban environments (Colvile et al., 2001; Querol et al., 2001; Ghose et al., 2004). These strategies intend to either reduce the number of vehicles circu- lating on conurbations or to mitigate the unitary emissions by vehicle, either using alternative fuels or new technology vehicles (hybrids, fuel cells, natural gas, biofuels, etc.) (e.g. Schultz et al., 2003; Stephens-Romero et al., 2009). A complementary way of reducing traffic emissions consists in changing the speed circula- tion patterns (Gonçalves et al., 2008; Keller et al., 2008). The speed dependency of emissions varies as a function of the pollutant, depending on the vehicle age, weight and cubic capacity of the engine. Therefore a unique optimal speed circulation for atmo- spheric pollutants for the whole range of vehicles in an urban vehicles fleet does not exist. Nevertheless, it is a widely adopted traffic management strategy, because its benefits concern not only pollutants emissions, but also reduces congestion, noise and acci- dents. The evaluation of air quality management strategies requires the use of measurements and air quality models to perform quantitative impact studies (Ponche and Vinuesa, 2005). On-road traffic modules included within emission inventories need more emissions measurements from vehicle types and pollution control * Corresponding author at: Environmental Modelling Laboratory, Technical University of Catalonia, Avda. Diagonal 647, Edificio H, Oficina 10.23, 08028 Bar- celona, Spain. Tel.: þ34 93 413 77 19. E-mail addresses: jose.baldasano@bsc.es (J.M. Baldasano), pedro.jimenezguerrero@ um.es (P. Jiménez-Guerrero). 1 Now at: Department of Physics, University of Murcia, Ed. CIOyN, Campus de Espinardo, 30100 Murcia, Spain. Tel.: þ34 868 88 8175. Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv ARTICLE IN PRESS 1352-2310/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2010.05.013 Atmospheric Environment xxx (2010) 1e10 Please cite this article in press as: Baldasano, J.M., et al., Air pollution impacts of speed limitation measures in large cities: The need for..., Atmospheric Environment (2010), doi:10.1016/j.atmosenv.2010.05.013