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Impact of anti-congestion policies on urban forms and environment.
In discussing the stakes of the new economic geography (NEG), Fujita and Krugman (2004) agreed that transportation costs are substantial to explain location decision of firms and households. Raising urban costs to internalize externalities of congestion may improve the allocation of resources but also have an impact on location decisions in the long run.
First, economists have assessed short-term consequences of implementing an urban toll, economists have focused on traffic, welfare effects, modal choice conditions and pricing equity (Eliasson and Mattson, 2006; Raux and Souche, 2004). They have also studied long-term effects regarding transport preferences and GHG emissions (Bhatt, 2011). Short-term consequences. In the seminal work of Solow (1972), the author determines a rent profile that is more convex in the case in which congestion is taken into account.
This means that rents become more expensive close to the CBD and relatively less at the edge of the city. Accordingly, households locate in smaller housing spaces near their workplace than at points farther away. Solow obtains a similar result in his subsequent paper in which he slightly changes the model (Solow, 1973). When congestion costs are introduced, land rents rise at all locations for a given city size. However, when housing density adjusts the city size expands. In the monocentric model, seven cases are analyzed where the pure distance costs and the congestion costs vary in the annual transportation cost function with the help of numerical simulations. The fraction of income spent on housing space after travel costs and the fraction of land allotted to residential use shift as well. When congestion costs are high, the diameter of the monocentric circular city increases gently. Some simulations are performed in which the fraction of land allotted to housing is low and increases from the CBD to the periphery. The simulations yield a flattening effect of the rent profile and a sprawling effect of the city boundary (Solow, 1972).
Solow (1972) is also concerned with the optimal fraction of land that can be allotted to the road system. In his seminal paper, he demonstrates that the best share between roads and housing is a fraction of land allocated to residential use yielding a minimum to the rent at the edge of the CBD. But his answer does not lead to an analytical solution, and he therefore leaves it for further research. Accordingly, in a subsequent study he carries out a cost-benefit analysis comparing shifts in the fraction of land use with the help of numerical simulations (Solow, 1973). Since no congestion tolls are implemented, land values represent diverse private transport costs. Households face a unique trade-off between rent and travel costs and do not take into account the social cost imposed to other families.
Numerical simulations are performed to compare three distinct planning decisions regarding the fraction of land devoted to housing and its effects on average annual rent, travel costs and welfare per household. The cost-benefit analysis leads to roads’ overcapacity within the city, especially close to CBD since market land values are distorted through the lack of a road-pricing scheme (Solow, 1973).
Regarding land use regulation in an urban model, a city planner is commonly used as a municipality for Solow (1972) or a manager for Arnott (1979). The former must choose the best allocation of land between roads and housing, and the latter must minimize its variable resource costs to supply the whole population in lot size, transportation and other goods consumed by each resident. Arnott (1979) demonstrates that transport improvement such as a road widening induces indirect costs that should be considered even though Solow (1973) ignored them. Indeed, it causes larger traffic flows than what existed previously and avoids an over-evaluation of land for both road and residential use. Transport upgrades in an unpriced road-scheme create a distorted urban economy in a long-run competitive equilibrium. Accordingly, indirect costs must be taken into account carefully in the cost-benefit analysis as it relates to optimal capacity allocated to roads.
Urban spatial structure, transport-related emissions and welfare.
In this first theoretical chapter11, we have studied the impacts of urban spatial structure on CO2 emissions stemming from transport flows and on welfare of households. To do so, we have built a theoretical model of a monocentric city and a polycentric city with an endogenous location of workplace. Within these spatial structures, location choice of households and their housing demand are determined endogenously. First, we analyze changes in CO2 emissions and welfare when a monocentric city shifts to a polycentric one with an endogenous secondary business district. Second, we assess our results extending our model with a larger supply of housing in the central business district in comparison with the SBD and by allowing wages to be determined endogenously within each business center.
Our chapter is related to previous theoretical works that have studied the development of secondary business districts in cities (Cavailh`es et al., 2007). Floater et al., (2014) and Burgalassi and Luzzati (2015), state that environmental impacts of urbanization depend on urban forms (design, density, etc.). Previous studies shed light on the benefits of the polycentric city as a spatial structure that would decrease the total distance traveled by workers and mitigate urban pollution (Gaign´e et al., 2012; Legras and Cavailh`es, 2016).
However, the literature does not assess the impact of a change in workplace location on carbon emissions when housing size is endogenous. In addition, the emergence of polycentric cities is microfounded when housing size reacts to a change in workplace location (Fujita and Ogawa, 1982; Anas and Kim, 1996; Lucas and Rossi-Hansberg, 2002). However, these authors have failed to address a major issue, namely, the impacts of job decentralization on transport-related pollution and welfare when housing size adjusts. Therefore, we develop our model to include both endogenous housing demand and decentralization of jobs. We find that decentralization of jobs within cities is not necessarily “the” strategy to reduce transport-related emissions and to improve welfare. Our analysis relies on the following trade-off. On the one hand, for a given population density, the average distance traveled by workers shrinks when the city shifts from a monocentric structure to a polycentric configuration. Hence, for a given housing size, job decentralization within cities decreases carbon emissions by making commuting trips shorter. This is true as long as the city border remains unchanged. On the other hand, the average housing size would increase when jobs are located on the edge of the city since the average price of land diminishes. As a consequence, the city border expands away from the city center and the average commuting distance may rise. The increasing housing demand may therefore counteract the positive effects of the emergence of secondary business districts on commuting distances and carbon emissions. Indeed, the net effect of this development on welfare depends on the characteristics of the transportation network within the city. More precisely, when housing size adjusts to urban forms through a change in land rents, a polycentric city is not desirable from welfare and ecological viewpoints when average travel speed and/or the number of roads directly connected with the inner city are low. More generally, our results show that the evaluation of urban policy effect on pollution emission must consider the long-run adjustments in housing size and density.
Efficiency of road pricing schemes with endoge- nous workplaces in polycentric city.
In this second theoretical chapter, the urban model builds on the one used in the first chapter to study the impacts of three road pricing schemes (Pigouvian tax, cordon toll and flat tax ) on the size of the CBD when two externalities (congestion and agglomeration) interplay in a polycentric city. Traffic congestion is modeled in line with the works of Arnott (2007), Verhoef (2005) and Tikoudis et al. (2015). First, the effects of road pricing schemes are evaluated within the monocentric city as a benchmark. Then, we focus on the changes in congestion level when a decentralization of jobs occurs. The size of the CBD as well as SBD are determined in equilibrium (“Laissez-faire”) and in optimum (a benevolent planner maximizes the welfare of inhabitants). Finally, we study the impacts of our three road pricing schemes in a polycentric city on congestion level, the size of the SBD and on aggregate welfare. We discuss the implementation of a second transport mode and car parks in the urban model in relation to tax effects.
Previous studies have often treated urban forms and traffic congestion separately when the monocentric city model has been used in theoretical contexts. A stream of literature has addressed the question of the optimum supply of road capacity in cities using the monocentric model with traffic congestion (Solow, 1972, 1974). Then, monocentric city models have been studied regarding the internalization of one or two externalities by Arnott (1979, 2007) and Wheaton (1998, 2004) in particular. More recently, several authors have focused on congestion management in partial equilibrium models of monocentric cities. A few authors have considered the polycentric city to analyze the impacts of urban congestion on wages, land rents, welfare and location choices of firms and households (Anas and Kim, 1996; Anas, 2013; Zhang and Kockelman, 2016a, 2016b). This literature is scarce and does not often deliver full analytical solutions. Numerical simulations are used to solve complex models, including a mix of labor market, production firms in cities, households, other firms and shopping centers of endogenous location with the externalities of congestion and agglomeration. In addition, we do not know precisely how the size of the CBD or SBD vary with road pricing schemes. To the best of our knowledge, this is the first study that delivers analytical solutions regarding the impacts of road pricing schemes on the size of the CBD when two externalities exist within a polycentric city.
Commuting and urban forms: case study of French municipality areas.
Finally, in this third chapter, we have collected data from the French national census to analyze the effects of urban forms on home-to-work distances and travel time during peak hours. Three periods are studied: 1999, 2007 and 2014. We use a distance meter called ”Odomatrix” which is a tool that measures road accessibility on the French network. Municipal data are combined with a road database from the National Institute for Geographic and Forestry Information (IGN). First, we define four measures of urban form. Our main concern is the spatial organization of workplaces and population within the French urban areas. In a second step, we specify an econometric model in order to evaluate the relevance and the magnitude of the relationship between these urban form measures and home-to-work distances over three periods. Third, we focus on the impacts of urban forms on peak hour travel times and distances between dwellings and workplaces only in 2014. Finally, we conduct an analysis of the relationship between urban form measures at the municipal level and commuting times and distances in 2014.
In France, average traveled distances increased between 1990 and 2014. This increase was mainly due to urban sprawl and segregation of urban functions (living spaces vs. workplaces) (Coud`ene and Levy, 2016). The same phenomenon is observed in Western economies (Kahn, 2010; Garcia-Palomares, 2010; Aguil´era et al., 2009). Urban densification is a current policy designed to reduce home-to-work distances and resulting energy consumption (transport, housing, etc.) (Larson and Yezer, 2015; Duranton and Turner, 2017; Blaudin de Th´e et al., 2018). However, the effects remain weak in the various empirical analyses. In addition, an increase in population density per square mile can lead to longer journey times (Priemus et al., 2001; Schwanen et al., 2004). Thus we consider focusing on the spatial organization of jobs within urban areas. We use four urban form measures as explanatory variables: (i) a ratio between the number of jobs in a central municipality and the total number of jobs in the urban area, (ii) a concentration index in the same vein as Herfindahl-Hirschmann, (iii) a spatial distribution index of population and jobs in the central municipalities and (iv) an index of the distribution of jobs and population within the municipalities of each urban area. Our objective is to determine those that are relevant in order to suggest a better targeting for urban policies.
Our econometric analyses yield a positive and significant relationship between the average traveled distances and the concentration of jobs in the central municipalities as well as in the urban areas where they are located. We obtain elasticities between commuting distances and jobs dispersion index between 0.22 and 0.26 for our cross-sectional analysis (1999, 2007 and 2014). Our analysis in 2014 yields relationships that are qualitatively similar.commuting times between dwellings and workplaces during rush hour. Our last counterfactual analysis confirms that if jobs and the labour force were equally distributed within an urban area, peak-hour travel times and home-to-work distances would decrease on average by 10% for the majority of municipalities, especially those located on the periphery. Our results highlight the significant elasticities between our dependent and explanatory variables but it would be necessary to test the causal effect of our urban forms measures by deepening our econometric analyses and experimenting a policy in situ.
Table of contents :
R´esum´e en fran¸cais
1.1 High congestion and pollution costs in urban areas across the globe.
1.2 Policies aiming to lower GHG emissions and congestion in urban areas.
1.3 Economic and environmental implications of different urban spatial structures
2 Literature review
2.1 Modeling the polycentric city
2.2 Impact of anti-congestion policies on urban forms and environment.
3.1 Chapter 1: Urban spatial structure, transport-related emissions and welfare
3.2 Chapter 2: Efficiency of road pricing schemes with endogenous workplaces in polycentric city
3.3 Chapter 3: Commuting and urban forms: case study of French municipality areas
1 Urban spatial structure, transport-related emissions and welfare.
2 A simple model
3 The monocentric city
4 The polycentric city
5.1 Extending the city vertically
5.2 Endogenous wage
5.3 Role of modal choice and congestion
2 Efficiency of road pricing schemes with endogenous workplaces in poly- centric city.
2 The model
2.1 The city
2.3 Congestion costs and transport infrastructure
2.4 Urban toll
3 The monocentric city
4 Decentralization of jobs and welfare
4.1 The polycentric city
4.2 Equilibrium allocation and optimal location of jobs
5 Polycentric city and road pricing schemes
6 Comparisons between road pricing schemes
6.1 Efficiency of the three road pricing schemes in the polycentric city .
7.1 Incidence of modal choice on congestion and urban structure
3 Mobilit´es pendulaires et formes urbaines: cas des aires urbaines fran¸caises m´etropolitaines.
2 Donn´ees sur les d´eplacements domicile-travail et les aires urbaines
2.1 D´eplacements domicile-travail
2.2 La mesure des formes urbaines
2.3 Les variables de contrˆole
3 ´Evolution des distances moyennes domicile-travail parcourues et formes urbaines
4 Temps de trajet `a l’heure de pointe et formes urbaines en 2014
4.1 Influence de l’aire urbaine
4.2 Niveau communal
List of tables
List of figures