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A Review of Travel by Design: The Influence of Urban Form on Travel
Regional Science and Urban Economics 32 (2002) 275–277 www.elsevier.com / locate / econbase
Book review A Review of Travel by Design: The Influence of Urban Form on Travel Edited by Marlon G. Boarnet and Randall Crane (Oxford University Press 2001) In 1990, Boston, Houston and Copenhagen had roughly the same per-capita Gross Regional Product, but car use per capita (measured in kilometers) was 10,280, 13,016 and 4,558, respectively (Newman and Kenworthy, 1999). Why is Houston a ‘‘car capital’’? Reducing vehicle dependence would lower carbon dioxide production, urban air pollution, congestion and slow farmland conversion. Could Houston become Copenhagen if we changed its urban form? This excellent book is organized around two major questions. First, ‘‘if we build cities and their suburbs differently, will their residents drive less? (page 10)’’. Chapter 3 provides a comprehensive overview of past research on this question and concludes that we do not know the answer. The literature review focuses on causality. If people who live in high density areas drive less, what have we learned about the causal impact of urban form on travel? A nice feature of this book is that it explicitly integrates micro economic theory into testing the book’s major hypothesis. In chapter 4, a detailed transportation modal choice model is presented using figures and algebra to highlight the tradeoffs. Walking is a transport technology featuring low fixed costs and rising marginal cost while driving features high fixed costs and lower marginal costs. Trip length plays a key role in determining what is the cost minimizing transport mode. New economists will benefit from seeing the analytic cases when ‘‘the new urbanism’’ is predicted to reduce vehicle dependence. The book is strong at pointing out unintended consequences of urban policy. ‘‘An implication for planners is that the built environment, if it is to reduce nonwork car trip making, should slow automobile speeds sufficiently to counteract the effect of any reduction in trip distances. Oddly, then, congestion can be an ally of planners who seek to eliminate auto mobile trips, as some reduction in trip speeds, possibly due to increases in 0166-0462 / 02 / $ – see front matter 2002 Published by Elsevier Science B.V. PII: S0166-0462( 01 )00087-4
Book review / Regional Science and Urban Economics 32 (2002) 275 – 277
276
congestion created by higher densities, can provide an incentive for persons to avoid driving (page 173).’’ Chapter 5 presents new evidence on the causal impact of urban form on transportation use. A detailed empirical analysis is presented based on data from 1986– 1993 from the Panel Study of Southern California Commuters Data. The main data is a travel diary over a two day period. The data set includes information on nonwork related trips, respondent demographics and respondent median car trip speed and distance. Using each respondent’s street address, local physical attributes of the community are constructed based on a ]14 mile ball surrounding the respondent’s place of residence. For example street network attributes are constructed as are landuse mix variables (percent of land in residential, commercial and vacant) and proxies for population density such as distance from the CBD. The dependent variable is non-work automobile trips. Multivariate regression models yield mixed results on the importance of urban form on transport. Based on the Los Angeles sample (see Table 5.4), there is no statistically significant relationship between the land-use variables and auto trips while based on the San Diego sample (see Table 5.5) land-use variables do matter. The regression results present new empirical findings on the importance of travel speed. Demand curves slope down! When drivers can drive faster, they take more trips. Thus, the authors conclude ‘‘When land use variables have an impact on non-work auto trip generation, that impact is through the effect on trip prices (speed and distance) (page 93).’’ It is relevant to note that the ‘‘urban-form’’ variables describes where the respondent lives not where the respondent is ‘‘going’’. Would the person have been more likely to take a bus if she was visiting an urban hospital rather than a suburban mall? Urban form can change the ‘‘full price’’ of travel by changing the speed that traffic can flow. But, there is little evidence that changes in the price of travel (such as rising oil prices) changes urban form. Richard Muth (1983) used the OPEC oil shock as a ‘‘natural experiment’’ and found no impact that this unexpected increase in gasoline prices changed the urban form and encouraged new migration to the center city. By purchasing more fuel efficient vehicles, drivers were able to lower the ‘‘full price’’ per mile of driving without moving residences. The second half of the book focuses on the supply of public transit accessible communities. How many households might choose to live in ‘‘New Urbanist’’ or similar neighborhoods? The authors argue that private developers will provide such housing if it is demanded but that local governments might impose obstacles to such developments. Chapters Six and Seven present a detailed analysis of the incentives of local communities in choosing how to zone land. Commercial use offers greater local tax revenue than residential use. Each community’s individually rational pursuit of tax revenue may impose an externality on the greater metropolitan area as reduced access to transit encourages vehicle dependence. An interesting case study of San Diego is presented in Chapter 8. The book provides neat details on the zoning of activities within a quarter mile of the San Diego trolley. At the Civic Center station, 0% of the land is zoned for residential use
Book review / Regional Science and Urban Economics 32 (2002) 275 – 277
277
while 57% of the land is zoned for commercial and one dominant nearby land use is a jail and government offices. The book could have delved deeper in its analysis of ‘‘the trouble with traffic’’. Are the externalities from having a ‘‘vehicle friendly’’ urban form growing larger or smaller over time? Chapter Two lays out the basics of why driving imposes social costs. This book’s subject matter becomes even more policy relevant if these costs are rising over time. Over the last 25 years, Los Angeles smog has fallen to the point where it is no longer the ‘‘smog capital’’ of the United States. While vehicle emissions and urban air pollution have fallen and this reduces the social marginal cost of local vehicle dependence, the social cost of congestion is likely to have increased as our value of time has increased. If a sprawled urban form encourages more driving trips and if there are large social costs caused by these trips, then there are significant costs to this urban form. But are the benefits of this urban form rising? The ‘‘New Urbanism’’ envisions a world where people live close to their employer. In this age of dual career ‘‘power couples’’ and decentralized employment, reducing vehicle access could hinder such couples’ job prospects in the local economy. Two married people may love their house but have very different human capital. Driving allows the two to access a range of different employers in the local market. As the population ages, there are more vehicle dependent senior citizens who do not want to walk their groceries home. The book’s graphics and photos distinguish it from the typical ‘‘dry’’ urban economics book. We see pictures of pedestrians in downtown Los Angeles in the 1930s and diagrams contrasting ‘‘sprawl’’ and ‘‘friendly’’ development. The community of Seaside, Florida is presented as an example of the ‘‘New Urbanism’’. This book successfully integrates qualitative and quantitative analysis. Given growing concern about urban quality of life and global climate change, this is a timely contribution. Students in planning departments and public policy programs will greatly benefit from reading this book which represents a balanced hybrid of urban economics and planning. Matthew E. Kahn Associate Professor of International Economics Fletcher School of Law & Diplomacy Tufts University Medford, MA 02155, USA References Muth, R., 1983. Energy Prices and Urban Decentralization. In: Downs, A., Bradbury, K. (Eds.), Energy Costs and Urban Development and Housing, Brookings Institution. Newman, P., Kenworthy, J., 1999. Sustainability and Cities; Overcoming Automobile Dependence, Island Press.
Book review A Review of Travel by Design: The Influence of Urban Form on Travel Edited by Marlon G. Boarnet and Randall Crane (Oxford University Press 2001) In 1990, Boston, Houston and Copenhagen had roughly the same per-capita Gross Regional Product, but car use per capita (measured in kilometers) was 10,280, 13,016 and 4,558, respectively (Newman and Kenworthy, 1999). Why is Houston a ‘‘car capital’’? Reducing vehicle dependence would lower carbon dioxide production, urban air pollution, congestion and slow farmland conversion. Could Houston become Copenhagen if we changed its urban form? This excellent book is organized around two major questions. First, ‘‘if we build cities and their suburbs differently, will their residents drive less? (page 10)’’. Chapter 3 provides a comprehensive overview of past research on this question and concludes that we do not know the answer. The literature review focuses on causality. If people who live in high density areas drive less, what have we learned about the causal impact of urban form on travel? A nice feature of this book is that it explicitly integrates micro economic theory into testing the book’s major hypothesis. In chapter 4, a detailed transportation modal choice model is presented using figures and algebra to highlight the tradeoffs. Walking is a transport technology featuring low fixed costs and rising marginal cost while driving features high fixed costs and lower marginal costs. Trip length plays a key role in determining what is the cost minimizing transport mode. New economists will benefit from seeing the analytic cases when ‘‘the new urbanism’’ is predicted to reduce vehicle dependence. The book is strong at pointing out unintended consequences of urban policy. ‘‘An implication for planners is that the built environment, if it is to reduce nonwork car trip making, should slow automobile speeds sufficiently to counteract the effect of any reduction in trip distances. Oddly, then, congestion can be an ally of planners who seek to eliminate auto mobile trips, as some reduction in trip speeds, possibly due to increases in 0166-0462 / 02 / $ – see front matter 2002 Published by Elsevier Science B.V. PII: S0166-0462( 01 )00087-4
Book review / Regional Science and Urban Economics 32 (2002) 275 – 277
276
congestion created by higher densities, can provide an incentive for persons to avoid driving (page 173).’’ Chapter 5 presents new evidence on the causal impact of urban form on transportation use. A detailed empirical analysis is presented based on data from 1986– 1993 from the Panel Study of Southern California Commuters Data. The main data is a travel diary over a two day period. The data set includes information on nonwork related trips, respondent demographics and respondent median car trip speed and distance. Using each respondent’s street address, local physical attributes of the community are constructed based on a ]14 mile ball surrounding the respondent’s place of residence. For example street network attributes are constructed as are landuse mix variables (percent of land in residential, commercial and vacant) and proxies for population density such as distance from the CBD. The dependent variable is non-work automobile trips. Multivariate regression models yield mixed results on the importance of urban form on transport. Based on the Los Angeles sample (see Table 5.4), there is no statistically significant relationship between the land-use variables and auto trips while based on the San Diego sample (see Table 5.5) land-use variables do matter. The regression results present new empirical findings on the importance of travel speed. Demand curves slope down! When drivers can drive faster, they take more trips. Thus, the authors conclude ‘‘When land use variables have an impact on non-work auto trip generation, that impact is through the effect on trip prices (speed and distance) (page 93).’’ It is relevant to note that the ‘‘urban-form’’ variables describes where the respondent lives not where the respondent is ‘‘going’’. Would the person have been more likely to take a bus if she was visiting an urban hospital rather than a suburban mall? Urban form can change the ‘‘full price’’ of travel by changing the speed that traffic can flow. But, there is little evidence that changes in the price of travel (such as rising oil prices) changes urban form. Richard Muth (1983) used the OPEC oil shock as a ‘‘natural experiment’’ and found no impact that this unexpected increase in gasoline prices changed the urban form and encouraged new migration to the center city. By purchasing more fuel efficient vehicles, drivers were able to lower the ‘‘full price’’ per mile of driving without moving residences. The second half of the book focuses on the supply of public transit accessible communities. How many households might choose to live in ‘‘New Urbanist’’ or similar neighborhoods? The authors argue that private developers will provide such housing if it is demanded but that local governments might impose obstacles to such developments. Chapters Six and Seven present a detailed analysis of the incentives of local communities in choosing how to zone land. Commercial use offers greater local tax revenue than residential use. Each community’s individually rational pursuit of tax revenue may impose an externality on the greater metropolitan area as reduced access to transit encourages vehicle dependence. An interesting case study of San Diego is presented in Chapter 8. The book provides neat details on the zoning of activities within a quarter mile of the San Diego trolley. At the Civic Center station, 0% of the land is zoned for residential use
Book review / Regional Science and Urban Economics 32 (2002) 275 – 277
277
while 57% of the land is zoned for commercial and one dominant nearby land use is a jail and government offices. The book could have delved deeper in its analysis of ‘‘the trouble with traffic’’. Are the externalities from having a ‘‘vehicle friendly’’ urban form growing larger or smaller over time? Chapter Two lays out the basics of why driving imposes social costs. This book’s subject matter becomes even more policy relevant if these costs are rising over time. Over the last 25 years, Los Angeles smog has fallen to the point where it is no longer the ‘‘smog capital’’ of the United States. While vehicle emissions and urban air pollution have fallen and this reduces the social marginal cost of local vehicle dependence, the social cost of congestion is likely to have increased as our value of time has increased. If a sprawled urban form encourages more driving trips and if there are large social costs caused by these trips, then there are significant costs to this urban form. But are the benefits of this urban form rising? The ‘‘New Urbanism’’ envisions a world where people live close to their employer. In this age of dual career ‘‘power couples’’ and decentralized employment, reducing vehicle access could hinder such couples’ job prospects in the local economy. Two married people may love their house but have very different human capital. Driving allows the two to access a range of different employers in the local market. As the population ages, there are more vehicle dependent senior citizens who do not want to walk their groceries home. The book’s graphics and photos distinguish it from the typical ‘‘dry’’ urban economics book. We see pictures of pedestrians in downtown Los Angeles in the 1930s and diagrams contrasting ‘‘sprawl’’ and ‘‘friendly’’ development. The community of Seaside, Florida is presented as an example of the ‘‘New Urbanism’’. This book successfully integrates qualitative and quantitative analysis. Given growing concern about urban quality of life and global climate change, this is a timely contribution. Students in planning departments and public policy programs will greatly benefit from reading this book which represents a balanced hybrid of urban economics and planning. Matthew E. Kahn Associate Professor of International Economics Fletcher School of Law & Diplomacy Tufts University Medford, MA 02155, USA References Muth, R., 1983. Energy Prices and Urban Decentralization. In: Downs, A., Bradbury, K. (Eds.), Energy Costs and Urban Development and Housing, Brookings Institution. Newman, P., Kenworthy, J., 1999. Sustainability and Cities; Overcoming Automobile Dependence, Island Press.