Gabriel Ahlfeldt lecturer at the London School of Economics, presents on the digital conversion of data derived from Olcott's Blue Books, the unique dataset of historical land values, land uses, building heights, and other information in Chicago and its suburbs, published annually between 1900 and 1990. The digitization project, which opens up new possibilities for statistical analysis of long-run adjustments in land values, involves using geographic information system (GIS) software to create a rectangular grid following Chicago's street pattern and produce a unique spatiotemporal dataset, providing insights into changes in the spatial structure of the city.
August 2012 Archives
Carlos Carrion and David Levinson (2012) Uncovering the influence of commuters' perception on the reliability ratio. (Working paper)
The dominant method for measuring values of travel time savings (VOT), and values of travel time reliability (VOR) is discrete choice modeling. Generally, the data sources for these models are: stated choice experiments, and revealed preference observations. There are few studies using revealed preference data. These studies have only used travel times measured by devices such as loop detectors, and thus the perception error of travelers has been largely ignored. In this study, the influence of commuters' perception error is investigated on data collected of commuters recruited from previous research. The subjects' self-reported travel times from surveys, and the subjects' travel times measured by GPS devices were collected. The results indicate that the subjects reliability ratio is greater than 1 in the models with self-reported travel times. In contrast, subjects reliability ratio is smaller than 1 in the models with travel times as measured by GPS devices.
Daniel Graham, Patricia Melo, and David Levinson (2012) Agglomeration, Accessibility, and Productivity: Evidence for Urbanized Areas in the US. (Working paper)
This paper undertakes an empirical analysis with the aim of improving the current understanding of the relationship between labor productivity and urban agglomeration economies across a sample of urbanized areas in the US. Agglomeration economies are represented with driving time measures of employment accessibility to establish a direct account for the link between transport and agglomeration economies. The paper investigates the presence of nonlinearities in the relationship between labor productivity and agglomeration economies, and examines the spatial decay pattern of the effects arising from this relationship. The findings indicate that there is considerable nonlinearity in the relation between productivity and transport induced agglomeration effects, implying that the estimation of country-level aggregate elasticities is likely to misrepresent the actual magnitude of any productivity gains from urban agglomeration. The results also suggest that the magnitude of the productivity-agglomeration effects decays very rapidly with time and is very strong within 20 minutes driving time. This suggests that knowledge spillover externalities are likely to be a very important Marshallian source of agglomeration economies.
JEL Classification: J31, R12, R40
Key words: agglomeration economies, network accessibility, labor productivity
Pavithra Parthasarathi and David Levinson (2012) Network structure and the journey to work: An intra-metropolitan analysis. (Working Paper)
This paper aims to look at the variation of network structure within a metropolitan area and relate it to observed travel, measured here as the average travel time to work. The Minor Civil Divisions (MCD) within the Twin Cities (Minneapolis, St. Paul) metropolitan area are chosen for this analysis. Quantitative measures, compiled from various sources, are used to capture the various aspects of network structure within each MCD. The variation of these measures within the metropolitan area is analyzed using spatial analyses. The measures of network structure are then related to observed travel using statistical regression models. The results confirm a relation between network structure and travel and point to the importance of understanding the underlying street network structure.
David J. Giacomin, Luke S. James, and David M. Levinson (2012) Trends in Metropolitan Network Circuity. (Working Paper)
Because people seek to minimize their time and travel distance (or cost) when commuting, the circuity–the ratio of network distance traveled to the Euclidean distance between two points–plays an intricate role in the metropolitan economy. This paper seeks to measure the circuity of the United States’ 51 most populated Metropolitan Statistical Areas and identify trends in those circuities over the time period from 1990- 2010. With many factors playing a role such as suburban development and varying economic trends in metropolitan areas over this timeframe, much is to consider when calculating results. In general, circuity is increasing over time.
Michael Iacono, David Levinson, Ahmed El-Geneidy, and Rania Wasfi (2012) Markov Chain Model of Land Use Change in the Twin Cities. (Working Paper)
The set of models available to predict land use change in urban regions has become increasingly complex in recent years. Despite their complexity, the predictive power of these models remains relatively weak. This paper presents an example of an alternative modeling framework based on the concept of a Markov chain. The model assumes that land use at any given time, which is viewed as a discrete state, can be considered a function of only its previous state. The probability of transition between each pair of states is recorded as an element of a transition probability matrix. Assuming that this matrix is stationary over time, it can be used to predict future land use distributions from current data. To illustrate this process, a Markov chain model is estimated for the Minneapolis-St. Paul, MN, USA (Twin Cities) metropolitan region. Using a unique set of historical land use data covering several years between 1958 and 2005, the model is tested using historical data to predict recent conditions, and is then used to forecast the future distribution of land use decades into the future. We also use the cell-level data set to estimate the fraction of regional land use devoted to transportation facilities, including major highways, airports, and railways. The paper concludes with some comments on the strengths and weaknesses of Markov chains as a land use modeling framework, and suggests some possible extensions of the model.
Carlos Carrion and David Levinson (2012) Route choice dynamics after a link restoration. (Working Paper)
Carrion and Levinson (2012) studied the bridge choice behavior of commuters before and after a new bridge opened to the public. This bridge replaced the previously collapsed I-35W bridge in the metro area of Minneapolis-St. Paul. The original I-35W bridge collapsed on August 1st, 2007, and the replacement bridge opened to the public on September 18th, 2008. This study extends Carrion and Levinson (2012) by considering explicitly the day-to-day behavior of travelers, and by also considering the previously excluded subjects that are transitioning between bridge alternatives not including the I-35W bridge. The primary results indicate that the subjects react to day-to-day travel times on a specific route according to thresholds. These thresholds help discriminate whether a travel time is within an acceptable margin or not, and travelers may decide to abandon the chosen route depending on the frequency of travel times within acceptable margins. The secondary results indicate that subjects previous experience, and perception of the alternatives also influence their decision to abandon the chosen route.
Paul Anderson, Andrew Owen, and David Levinson (2012) The Time Between: Continuously-defined accessibility functions for schedule-based transportation systems. (Working paper)
Accessibility is traditionally considered to be a property of a point or region in space, and to be invariant over time (or at least over some computationally convenient time interval). How- ever, a locations accessibility can vary over time on a wide range of scales. This temporal variation is especially significant for schedule-based transportation systems. Current measures of accessibility generally reflect the accessibility only at points in time corresponding to the departures of one or more trips; accessibility between these time points remains unconsidered and undefined. Consequently, these measures are insensitive to changes in route frequency and the distribution of trip departure times. Furthermore, these approaches ignore the disutility experienced by a system user who is limited to departing or arriving at scheduled times rather than at preferred times. As a result, they systematically overestimate the accessibility experienced by users of scheduled transportation systems. We establish new methods for representing the accessibility provided by a schedule-based transportation system from a specific location as a continuously-defined accessibility function (CDAF) of desired departure time, defined for all time points. Using schedule and route information from metropolitan transit providers, we demonstrate the application of these methods to gain new insight into the accessibility provided by real-world transportation systems. Four examples are developed to represent common service types in metropolitan transit networks. The results confirm that accessibility is significantly overestimated by measuring single points and show that trip frequency is more valuable for sustained accessibility than high accessibility on individual trips.
Pavithra Parthasarathi, David Levinson, and Hartwig Hochmair (2012) Network Structure and Travel Time Perception. (Working Paper, Presented at the 2012 International Association of Travel Behavior Research Conference in Toronto)
Road networks have an underlying structure. This structure is defined by the layout, arrangement and the connectivity of the individual network elements, the road segments and their intersections. The differences in network structure exist across and within networks. Travelers perceive and respond to these differences in underlying network structure and complexity. This paper extends the analysis to understanding the underlying theory of why network structure influences travel. Specifically the focus is on the influence of network structure on travel time perception. The hypothesis here is that network design influences traveler perceptions, more specifically the perceptions of travel distance and time. This perception of travel distance and time in turn influences the actual travel by affecting choice of destination, mode, route, and whether to engage in activities.
Xuan Di, Henry Liu, and David Levinson. (2012) Multi-agent Route Choice Game for Transportation Engineering. (Working paper)
In undergraduate transportation engineering courses, traffic assignment is a difficult concept for both instructors to teach and for students to learn, because it involves many mathematical derivations and computations. We have designed a multiplayer game to engage students in the process of learning route choice, so that students can visualize how the traffic gradually reach user equilibrium (UE). For one scenario, we employ a Braess' Paradox, and explore the phenomenon during the game-play. We have done the case-control and before-after comparisons. The statistical results show that, students who played the game improve their understanding of the Braess' Paradox more than those who did not play. Among game players, younger students benefit more in their learning; while those who are not comfortable with exploring a phenomenon on their own think this game not as effective as those who prefer hands-on learning experiences.
Chris Urmson @ Official Google Blog: The self-driving car logs more miles on new wheels:
"Our vehicles, of which about a dozen are on the road at any given time, have now completed more than 300,000 miles of testing. They’ve covered a wide range of traffic conditions, and there hasn’t been a single accident under computer control.
We’re encouraged by this progress, but there’s still a long road ahead. To provide the best experience we can, we’ll need to master snow-covered roadways, interpret temporary construction signals and handle other tricky situations that many drivers encounter. As a next step, members of the self-driving car team will soon start using the cars solo (rather than in pairs), for things like commuting to work. This is an important milestone, as it brings this technology one step closer to every commuter. One day we hope this capability will enable people to be more productive in their cars. For now, our team members will remain in the driver’s seats and will take back control if needed.
And while these team members are commuting, many of them will be testing our algorithms on a new type of vehicle we’ve added to the self-driving car family over the past few months to help us refine our systems in different environments and on different terrain: the Lexus RX450h.
Michael Iacono and David Levinson (2012) Rural Highway Expansion and Economic Development: Impacts on Private Earnings and Employment. (Working paper)
With the interstate system substantially complete, the majority of new investment in highways is likely to take the form of selective capacity expansion projects in urban areas, along with incremental expansions and upgrades to expressway or freeway standards of existing intercity highway corridors. This paper focuses specifically on the latter type of project, rural highway expansions designed to connect smaller outstate cities and towns, and examines their effects on industry-level private earnings and local employment. We examine three case study projects in rural Minnesota and use panel data on local earnings and employment to estimate the impacts of the improvements. Our results indicate that none of the projects studied generated statistically significant increases in earnings or employment, a finding we attribute to the relatively small time savings associated with the projects and the maturity of the highway network. We suggest that for rural highway expansion projects, as with other types of transportation projects, user benefits should be a primary evaluation criterion rather than employment impacts.
Carlos Carrion, Nebiyou Tilahun, and David Levinson (2012) Monte Carlo Simulation of Adaptive Stated Preference Survey with a case study: Effects of Aggregate Mode Shares on Individual Mode Choice. (Working Paper)
Monte Carlo experiments are used to study the unbiasedness of several common random utility models for a proposed adaptive stated preference survey. This survey is used to study the influence of the knowledge of existing mode shares on travelers mode choice. Furthermore, the survey is applied to a sample of subjects selected from the University of Minnesota. The results indicate that the presence of mode shares in the mode choice model does influence the decision of travelers. The estimates are found to be biased by the Monte Carlo experiments.
Andrew Owen, Paul Anderson, and David Levinson (2012) Relative Accessibility and the Choice of Modes. (Working Paper).
The factors influencing commute mode choice are a subject of ongoing research and policy. Existing literature explores a wide range of factors which may influence mode choice; many of these focus on demographic factors as well as user preferences and perception, thereby highlighting the unique characteristics of each mode. This analysis hypothesizes that mode share, the aggregate expression of individuals' mode choices, is determined in large part by more fundamental properties of transportation systems. Accessibility, which measures the ease of reaching destinations, is used as a tool for comparing modes which focuses on their properties as abstract transportation systems. It explores the potential to predict the relative commute shares of non-auto and auto modes from the relative accessibility provided by each. Using public data sources and methods selected for their simplicity and ease of interpretation, a model is estimated which accounts for 41% of the variation in commute mode share at the block group level in the Minneapolis--Saint Paul, MN metropolitan area.fixed broken link - 1:31pm