Evaluating the impact of urban mobility policies on the air quality levels of Barcelona by means of an integrated modelling system

Persistent high levels of NO2 have severe health effects on population. These are often found in large urban conurbations with high vehicle densities. In Barcelona, with one of the highest vehicle densities in Europe, the two traffic air quality monitoring stations are continuously exceeding the limit values established by the 2008/50/EC Ambient Air Quality Directive. To reduce traffic emissions and associated air pollution levels, Barcelona is applying a series of traffic restrictions that attempt to renew and reduce the amount of circulating vehicles within the city. These include the reduction of private vehicle space in specific areas or urban corridors of the city (superblocks and tactical urbanism) and the implementation of a Low Emission Zone (LEZ) that restricts the entrance of most polluting vehicles in the city. In order to quantify and evaluate the level of effectiveness of the applied restrictions, air quality modelling is presented as a necessary tool to complement the information provided by the air quality monitoring stations. In this sense, the present thesis evaluates the impact that the different restrictions have on the resulting NOx emissions and NO2 concentration levels in Barcelona. To accomplish that, we developed an integrated air quality system composed by the VISUM traffic simulator, the emission model HERMESv3 and the street-scale dispersion model CALIOPE-Urban, which integrates the mesoscale CALIOPE air quality forecast system and the Gaussian dispersion model R-LINE. The thesis first explains the coupling, calibration and validation process of the traffic-emission system. This is followed by an emission sensitivity analysis of typically high uncertainty emission features such as different approaches in regard of vehicle fleet composition, public bus transport implementation, temperature effect or the application of non-exhaust PM sources. We also explore the limitations of the developed macroscopic system by comparing it with a microscopic -highly detailed- approach composed by the microscopic traffic simulator Aimsun Next and the PHEMLight vehicle emission model. Finally, we explain the coupling of the traffic-emission system with the mesoscale CALIOPE and street-scale CALIOPE-Urban air quality systems. In this study, we apply the traffic restrictions previously mentioned in Barcelona to observe their effects in traffic routing, traffic emissions and resulting air quality levels at a resolution of 20 meters. Our results show that the only measures with an overall reduction on NOx emissions are the ones considering the LEZ or a reduction on the traffic demand of -25%. The combination of all strategies with the demand reduction shows the highest NOx emission decrease (-30%) while if traffic demand is kept constant, the computed NOx reductions are of -13%. The strategies limited to restrict the vehicle space on the city show a negligible impact on the overall traffic emissions (+0.1%), although they generate important street-level emission gradients, up to +/-17% in NOx. The impact on NO2 air quality levels follows the same pattern as for emissions. The scenarios comprising the LEZ and the -25% demand reduction show the highest NO2 reductions (-5 to -10 and -10 to -20 ug/m3 in daily average NO2 concentration values). The unique application of traffic measures limiting the vehicle space show limited impacts of +/-5 ug/m3 due to traffic re-routing, as previously commented. Considering the obtained results, the reductions achieved are insufficient to ensure compliant air quality levels, and are very far from reaching the new WHO air quality guideline values. The applied restrictions must be accompanied by a larger decrease in the total number of circulating vehicles throughout the city which could be achieved, for instance, by the application of a congestion charge, or the implementation of local zero emission zones similar to the ones that are currently being deployed in the city of London.La persistente acumulación de altos valores de NO2 presenta serios problemas de salud. Esto ocurre con frecuencia en grandes zonas urbanas con altas densidades de tráfico. En Barcelona, con una de las mayores densidades de vehículos de Europa, las dos estaciones monitoreo de calidad del aire de tráfico exceden de forma continuada los valores limite establecidos por la 2008/50/EC Ambient Air Quality Directive. Para reducir las emisiones de tráfico Barcelona esta aplicando una serie de restricciones al tráfico con el propósito de renovar y reducir la cantidad de vehículos circulante. Estas medidas incluyen la reducción de espacio al vehículo privado en áreas específicas o en corredores de la ciudad (Supermanzanas o urbanismo táctico) y la implementación de una Zona de Bajas Emisiones (ZBE) que restringe la entrada a los vehículos mas contaminantes. Para cuantificar y evaluar el nivel de eficacia de las restricciones mencionadas, la modelización de calidad del aire se presenta como una herramienta necesaria para complementar la información dada por las estaciones de monitoreo de calidad del aire. Esta tesis evalúa el impacto que las diferentes restricciones tienen en los valores de emisión de NOx y de concentración de NO2 en Barcelona. Para ello, hemos desarrollado un sistema de calidad del aire compuesto por el simulador de tráfico VISUM, el modelo de emisiones HERMESv3 y el modelo de dispersión urbana CALIOPE-Urban, que integra el sistema mesoescalar de calidad del aire CALIOPE y el sistema Gaussiano de dispersión R-LINE. En la tesis se detalla el acoplamiento y el proceso de calibración y validación del sistema de tráfico-emisiones. A continuación, se realiza un estudio de sensibilidad valorando diferentes aproximaciones de variables de alta incertidumbre para la estimación de emisiones tales como la composición vehicular, la implementación del transporte público, el efecto de la temperatura o la consideración de fuentes PM no provenientes del gas de escape. También exploramos las limitaciones del sistema macroscópico desarrollado comparándolo con un sistema de alto detalle compuesto por el simulador micro Aimsun Next y el modelo de emisiones vehiculares PHEMLight. Finalmente, explicamos el acoplamiento del sistema tráfico-emisiones con el sistema de calidad del aire mesoescalar CALIOPE y el urbano CALIOPE-Urban que usamos para evaluar las restricciones de tráfico antes mencionadas en Barcelona y observar sus efectos en las rutas de tráfico, emisiones y concentración a una resolución de 20 metros. Los resultados muestran que las únicas medidas con una reducción global de emisiones NOx son las que consideran la ZBE o una reducción de demanda del -25%. La combinación de todas las estrategias con la reducción de demanda muestra las mayores reducciones en NOx (-30%) mientras que si la demanda se mantiene constante las reducciones observadas son del -13%. Las estrategias que se limitan a restringir el espacio del vehículo muestran reducciones negligibles (+0.1%), aunque generan importantes gradientes a nivel de calle que pueden llegar al +/-17% en NOx. El impacto en los valores de concentración de NO2 sigue los mismos patrones que las emisiones. Los escenarios que comprenden la ZBE y la reducción de demanda del -25% muestran las mayores reducciones (-5 a -10 y -10 a -20 ug/m3 de NO2). La consideración de las medidas que únicamente limitan el espacio al vehículo muestran reducciones de NO2 de +/-5 ug/m3 debido a la redistribución de rutas de tráfico. Concluimos que las reducciones obtenidas son insuficientes para asegurar valores de calidad del aire conforme a los límites de la UE, y están muy lejos de llegar a los nuevos valores guía de la OMS. Las restricciones aplicadas deben ir acompañadas por un mayor descenso del total de vehículos circulantes que podría conseguirse, por ejemplo, mediante la aplicación de un peaje de congestión o la implementación de zonas de cero emisiones, similares a las que se están desplegando actualmente en la ciudad de LondresPostprint (published version

Commuting practices:new insights into modal shift from theories of social practice

The automobile commute makes an important contribution to carbon emissions but has proven stubbornly resistant to modal shift policy initiatives. In this paper we use theories of social practice to develop insights into why this stubbornness might exist, and what might help accelerate transitions to bus- and cycle-commuting. By analysing qualitative data about everyday mobility in two UK cities, we examine how the availability of the constituent elements of bus- and cycle-commuting practices is crucial for modal shift to occur, but they are often absent. We also draw attention to time-space contingencies that render recruitment to low-carbon commuting practices more or less likely, including how commuting is sequenced with other social practices and how the sites of these practices interact with the affordances, and spatial infrastructure, of bus- and cycle-commuting. These insights lead us to argue that choice and land use planning focussed policy initiatives designed to invoke modal shift need to coexist in integrated policy configurations with initiatives designed to reshape both mobility and non-mobility practices. This means addressing the structural barriers caused by the lack of availability of the elements that constitute bus- and cycle-commuting, and intervening in the timing and spatiality of a range of social practices so as to reduce the tendency for commutes to have spatial and temporal characteristics that militate against the use of bus and cycle modes

Rethinking Streets: a study of streetspace allocation metrics and street networks in London

This research investigates streetspace allocation metrics for all streets in London providing quantitative evidence about a key parameter of street design citywide. A new methodology to quantify streetspace allocation is introduced using a geocomputational approach that allows both the processing of high-resolution topographic data over a large geographic extent and enables replicability for other cities. The correlation between streetspace allocation metrics and street network centrality at distinct scales is investigated across different geographic areas. These variables are then examined using cluster analysis to identify a typology of streets based on streetspace allocation and centrality. The results provide the framework for a design scenario study of inner London applying shortest-path analysis under an active travel prioritisation perspective. Streetspace statistics for London confirm the predominance of space allocated for vehicular transport over pedestrian uses. Most streets display standard "residential" street metrics, coinciding with traditional street classification schemes. Also, this serves to demonstrate quantitatively the spatially efficient organisation of the London street system with few wider distributors and many narrower local streets. In addition, through the combined examination of the streets' allocation and configurational metrics, it is possible to identify a new sub-type of local streets. The spatial arrangement of the streets segments types follows a centre-periphery pattern: wider and higher centrality streets are clustered at the city centre and show relative larger streetspace designated to pedestrians, corresponding with higher levels of estimated activity. On a prescriptive streetspace model of Inner London, the streetspace allocation of critical pathways is modified to illustrate how strategic scale street properties affect and are affected by design scale street parameters. The fine-grain physical metrics analysed here, not only can be useful to tackle a wide range of contemporary street related questions from urban environmental quality to the adoption of new technologies but also offer alternative analytical methods for street research, planning and design

Passenger Flows in Underground Railway Stations and Platforms, MTI Report 12-43

Urban rail systems are designed to carry large volumes of people into and out of major activity centers. As a result, the stations at these major activity centers are often crowded with boarding and alighting passengers, resulting in passenger inconvenience, delays, and at times danger. This study examines the planning and analysis of station passenger queuing and flows to offer rail transit station designers and transit system operators guidance on how to best accommodate and manage their rail passengers. The objectives of the study are to: 1) Understand the particular infrastructural, operational, behavioral, and spatial factors that affect and may constrain passenger queuing and flows in different types of rail transit stations; 2) Identify, compare, and evaluate practices for efficient, expedient, and safe passenger flows in different types of station environments and during typical (rush hour) and atypical (evacuations, station maintenance/ refurbishment) situations; and 3) Compile short-, medium-, and long-term recommendations for optimizing passenger flows in different station environments

Modelling for sustainable cities: Conceptual approach and an audit of existing sectoral models for transport, air pollution, land use, and population modelling.

Urban modelling theories and operational models date back to the sixties and seventies, and have been constantly improved since then. It seems therefore that there should be no problem with addressing city sustainability issues. After all, these models claimed to be tools to help planners in choosing the best policies, exactly the same objectives that we need sustainability models to fulfil. The problem is that urban models have ignored many problems considered today as most pressing. They have not only ignored environmental issues, but also most quality of life issues. If we look at diagrams by Wilson (1981, p.265; 1977, p.3) or Wegener (1994), it is clear that these models focus on land use (understood as location and intensity of activities) and transport problems. The name “urban model” might be then misleading. This does not mean that environmental problems were not modelled at all: they were, but this research area was outside the interests of urban researchers and planners. One possibility for the way forward is to use old models, integrate them and extend them to include missing components. In order to do this, one should first specify the components to be included in the integrated model, taking the sustainability concept and the new modelling objectives as a point of reference

Dockless micromobility sharing in Calgary: A spatial equity comparison of e-bikes and e-scooters

This paper reports on a comparison of the spatial equity dimensions of dockless bike and e-scooter sharing in Calgary, Alberta. Using trip data from the City of Calgary’s Shared Mobility Pilot (between July-September 2019), this study investigates differences in micromobility utilization by dockless mode between areas characterized by different levels of deprivation. ANOVA and linear regression results show that utilization of both dockless modes was spatially inequitable, with e-scooter and dockless bike trips concentrated in the least deprived areas. Dockless bike and e-scooter sharing utilization declined with each increase in deprivation level by 0.138 trips per 1,000 persons per vehicle for dockless e-scooters, and 0.015 trips per 1,000 persons per vehicle for dockless bikes, suggesting that more equity considerations are required to ensure that the benefits of dockless micromobility sharing are available to all areas regardless of the relative advantage or disadvantage.Cet article rend compte d’une comparaison des dimensions d’équité spatiale du partage de vélos et de scooters électriques sans quai à Calgary, en Alberta. À l’aide des données sur les déplacements du projet pilote de ‘mobilité partagée’ de la ville de Calgary (entre juillet et septembre 2019), cette étude examine les différences d’utilisation de la micromobilité en mode sans quai entre les zones caractérisées par différents niveaux de privation. Les résultats de l’ANOVA et de la régression linéaire montrent que l’utilisation des deux modes sans quai était spatialement inéquitable, et de même que spatialement inéquitable, tant les déplacements en scooter électrique et en vélo sans quai étant concentrés dans les zones les moins défavorisées. L’utilisation du partage de vélos et de scooters électriques sans quai diminue à chaque augmentation du niveau de privation de 0,138 trajets pour 1 000 personnes par véhicule pour les scooters électriques sans quai et de 0,015 trajets pour 1 000 personnes par véhicule pour les vélos sans quai. Ce qui suggère que davantage de considérations d’équité sont nécessaires pour garantir que les avantages du partage de la micromobilité sans quai sont disponibles dans toutes les régions, quel que soit l’avantage ou le désavantage relatif

Book of abstracts of the 24th Euro Working Group on Transportation Meeting

Sem resumo disponível.publishe

A social vulnerability-based genetic algorithm to locate-allocate transit bus stops for disaster evacuation in New Orleans, Louisiana

In the face of severe disasters, some or all of the endangered residents must be evacuated to a safe place. A portion of people, due to various reasons (e.g., no available vehicle, too old to drive), will need to take public transit buses to be evacuated. However, to optimize the operation efficiency, the location of these transit pick-up stops and the allocation of the available buses to these stops should be considered seriously by the decision-makers. In the case of a large number of alternative bus stops, it is sometimes impractical to use the exhaustive (brute-force) search to solve this kind of optimization problem because the enumeration and comparison of the effectiveness of a huge number of alternative combinations would take too much model running time. A genetic algorithm (GA) is an efficient and robust method to solve the location/allocation problem. This thesis utilizes GA to discover accurately and efficiently the optimal combination of locations of the transit bus stop for a regional evacuation of the New Orleans metropolitan area, Louisiana. When considering people’s demand for transit buses in the face of disaster evacuation, this research assumes that residents of high social vulnerability should be evacuated with high priority and those with low social vulnerability can be put into low priority. Factor analysis, specifically principal components analysis, was used to identify the social vulnerability from multiple variables input over the study area. The social vulnerability was at the census block group level and the overall social vulnerability index was used to weight the travel time between the centroid of each census block to the nearest transit pick-up location. The simulation results revealed that the pick-up locations obtained from this study can greatly improve the efficiency over the ones currently used by the New Orleans government. The new solution led to a 26,397.6 (total weighted travel time for the entire system measured in hours) fitness value, which is much better than the fitness value 62,736.3 rendered from the currently used evacuation solution