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Browsing by Author "Cui, Mengying"

Now showing 1 - 12 of 12
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    Accessibility Analysis of Risk Severity
    (2015) Cui, Mengying; Levinson, David, M
    Risk severity in transportation network analysis is defined as the effects of a link or network failure on the whole system. Change accessibility (reduction in the number of jobs which can be reached) is used as an integrated indicator to reflect the severity of a link outage. The changes of accessibility before-and-after the removing of a freeway segment from the network represent its risk severity. The analysis in the Minneapolis - St. Paul (Twin Cities) region show that links near downtown Minneapolis have relative higher risk severity than those in rural area. The geographical distribution of links with the highest risk severity displays the property that these links tend to be near or at the intersection of freeways. Risk severity of these links based on the accessibility to jobs and to workers at different time thresholds and during different dayparts are also analyzed in the paper. The research finds that network structure measures: betweenness, straightness and closeness, help explain the severity of loss due to network outage.
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    Accessibility and the Ring of Unreliability
    (2016) Cui, Mengying; Levinson, David, M
    This study measures the variability of job accessibility via automobile for the Minneapolis-St. Paul region. The accessibility analysis uses cumulative opportunity measures. The travel times on the network are tested at various level (10th percentile speed, 50th percentile speed, 90th percentile speed) using the TomTom speed data for 2010. It is shown that accessibility varies widely day-to-day as travel speeds on the network vary. Some parts of the region (a ring around the core) have more volatility in accessibility (and are thus less reliable) than others.
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    Agglomeration Economies
    (Center for Urban and Regional Affairs, University of Minnesota, 2010-01) Cao, Jason; Iacono, Michael; Levinson, David; Cui, Mengying
    Economists have long recognized the importance of urban areas as focal points of economic production and exchange. In recent decades, they have also come to better understand the productivity benefits of firms being located in large urban areas. A variety of advantages may accrue to firms that cluster together in large cities relating, for example, to access to specialized labor, information spillovers, and interactions with customers or suppliers. These types of advantages are often referred to as examples of agglomeration economies in urban areas. Empirically, these gains have been shown to be potentially quite large, with reviews of the literature suggesting that doubling the size of an urban area’s population may be associated with productivity gains on the order of several percentage points. While economic research on this topic has greatly advanced our understanding of the concepts, theory, and likely quantitative implications for urban economies, there has been comparatively little emphasis on the spatial nature of agglomeration economies within urban areas. This is an important distinction, as different sources of agglomeration economies may have different spatial characteristics, and some may be sensitive to transport costs in ways that can be affected by the performance of urban transportation networks. Our research was an effort to link these concepts by operationalizing two specific types of agglomeration economies, localization and urbanization economies, and to investigate their relationship to employment density across several economic sectors within the Twin Cities.
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    Full Cost Accessibility
    (2018-06) Cui, Mengying
    Accessibility measures the ease of reaching destinations, and is the product of a function of the cost of travel between two points and the number of opportunities at the destination. That cost is usually represented as individual travel time, and occasionally as time and out-of-pocket monetary costs. Thus, it fails to fully capture travel costs, especially the external costs, of travel. This study develops a full cost accessibility (FCA) framework combining the internal and external cost components of travel with accessibility evaluations, to provide an efficient evaluation tool for transport planning projects. The FCA framework includes three major steps: analyzing cost components of travel, proposing new path types, and performing FCA analysis. The cost analysis distinguishes the internal and external costs of travel for alternate cost components and proposes a link-based cost model applied to each road segment in a metropolitan road network. The new path types, including the Safest and Greenest/Healthiest paths, in addition to the traditional Shortest Travel Time and Cheapest (least expensive) paths, are proposed to translate link costs into trip costs by selecting the routes with the lowest cost. For the FCA analysis, we measure the number of opportunities that can be reached in a given cost threshold. The key cost components for travelers are categorized as time costs, safety costs, emission costs, and monetary costs. The Minneapolis - St. Paul Metropolitan (Twin Cities) region was selected as the study area to implement the FCA framework based on each of those key cost components. Our major findings indicate: 1. The average full cost of travel is $0.68/veh-km in the Twin Cities region. Time and monetary costs account for approximately 85% of the total. It is unlikely that travelers will shift their route significantly to consider safety and emissions. 2. Except for the infrastructure cost, highways are more cost-effective than other surface roadways considering all the other cost components, and the internal and full costs. 3. Most new path types show largely the same spatial distribution as the shortest travel time path. However, the healthiest path, concerning the emission intake cost, detours to exurban areas where the on-road concentrations are lower; the lowest infrastructure cost path detours to local surface roadways where the infrastructure expenses are lower. 4. Job accessibility measurements based on different cost components show similar spatial distribution patterns. Accessibility decreases with the distance to the downtown area. Slight differences exist depending on the properties of cost components. 5. Accessibility difference assessment reveals a cost-benefit trade-off showing that travelers will save $0.24/veh-km of full cost on average based on the lowest full cost path rather than the shortest travel time path by paying a time-weighted accessibility loss of 191 jobs. This dissertation demonstrates the practicability of FCA framework in metropolitan areas.
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    Full cost accessibility
    (Journal of Transport and Land Use, 2018) Cui, Mengying; Levinson, David
    Traditional accessibility evaluation fails to fully capture the travel costs, especially the external costs, of travel. This study develops a full cost accessibility (FCA) framework by combining the internal and external cost components of travel time, safety, emissions, and money. The example illustrated compares FCA by automobile and bicycle on a toy network to demonstrate the potential and practicality of applying the FCA framework on real networks. This method provides an efficient evaluation tool for transport planning projects.
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    Full cost analysis of accessibility
    (2016-08-01) Cui, Mengying; Levinson, David M
    Traditional accessibility evaluation fails to fully capture the travel costs, especially the external costs of travel. This study develops a framework of extending accessibility analysis combining the alternate (internal and external) cost components of travel, time, safety, emission and money, with accessibility analysis, which makes it an efficient evaluation tool for the potential needs of transport planning projects. An illustration of this framework based on a toy network was also built in this paper, which proves the potential of applying the extending accessibility analysis into the network of metropolitan areas.
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    The Greenest Path: Comparing the Effects of Internal and External Costs of Motor Vehicle Pollution on Route Choice and Accessibility
    (2016-08-01) Cui, Mengying; Levinson, David M
    On-road emissions are a dominant source of urban air pollution, which damages human health. The "greenest path" is proposed as an alternative pattern of traffic route assignment to minimize the costs of emissions or exposure, pursues an environmentally optimal. The framework of a link-based emission cost analysis is built for both internal and external environmental costs and applied to the road network of the Twin Cities Metropolitan area based on the EPA MOVES model. The greenest (internal/external) path is skimmed for all OD pairs to compare the work trip flows on the roads and accessibility distribution. It is shown that the emission cost that travelers impose on others is greater than which they bear. Considering only external emissions costs thus produces a lower accessibility than considering only internal emissions costs. This research contributes to understanding the full cost of travel.
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    The Healthiest vs. Greenest Path: Comparing the Effects of Internal and External Costs of Motor Vehicle Pollution on Route Choice
    (2017) Cui, Mengying
    On-road emissions, a dominant source of urban air pollution, damage human health. The 'healthiest path' and the 'greenest path' are proposed as alternative patterns of traffic route assignment to minimize the costs of pollution exposure and emission, respectively. As a proof-of-concept, the framework of a link-based emission cost analysis is built for both internal and external environmental costs and is applied to the road network in the Minneapolis - St. Paul Metropolitan Area based on the EPA MOVES and RLINE models. The healthiest and the greenest paths are skimmed for all work-trip origin-destination pairs and then aggregated into work trip flows to identify the healthier or greener roads in a comparative statics analysis. The estimates show that highways have higher emission concentrations due to higher traffic flow, on which, but that the internal and external emission costs are lower. The emission cost that commuters impose on others greatly exceeds that which they bear. In addition, the greenest path is largely consistent with the traditional shortest path which implies that highways tend to be both greener and shorter (in travel time) for commuters than surface streets. Use of the healthiest path would generate more detours, and higher travel times.
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    The Impacts of Transportation Investment on Economic Growth in the Twin Cities
    (Center for Transportation Studies, University of Minnesota, 2016-06) Cao, Jason; Iacono, Michael; Levinson, David; Cui, Mengying
    The transportation system plays a critical role in fostering economic growth. Although previous studies have shed light on the impacts of transportation investments, their results are not readily adapted to predicting economic impacts of individual transportation projects. This study aimed to (1) investigate the impacts of transportation investments on economic growth (wages and employment) in the Twin Cities and (2) develop a method that practitioners can apply to predict economic growth resulting from investments in individual projects (as well as disinvestments). The capacity of such predictions is critical for the economy of the Twin Cities because transportation infrastructure lasts for decades once built. The method is expected to be used by practitioners of planning, programming, and finance at MnDOT and DEED, as well as at the Metropolitan Council. This study contributes to the base of knowledge by offering new empirical evidence on intra-urban patterns of agglomeration based on small-scale geographic data on job density from the Twin Cities. Our findings indicate that in general urbanization effects tend to dominate localization effects across a range of industries.
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    Intraurban Accessibility and Employment Density
    (2006-08-01) Iacono, Michael J; Cao, Jason X; Cui, Mengying; Levinson, David M
    This study investigates the relationship between urban accessibility and firm agglomeration, as reflected in patterns of urban employment densities. We use measures of accessibility derived from the regional highway network, combined with small-scale (Census block-level) data on employment from the Longitudinal Employer-Household Dynamics (LEHD) data set to generate proxies for different sources of agglomeration, specifically urbanization and localization economies. These variables are employed in a set of employment density regressions for 20 two-digit NAICS code sectors to identify the propensity of each sector to agglomerate in response to varying levels of accessibility. The density regressions are applied to sample data from the Minneapolis-St. Paul, Minnesota (Twin Cities) metropolitan region for the years 2000 and 2010. We find that in general urbanization effects tend to overshadow those of localization effects. Moreover, these effects tend to vary by sector, with many service-based sectors showing a stronger propensity to agglomerate than manufacturing and several "basic" sectors like agriculture, mining and utilities.
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    Measuring full cost accessibility by auto
    (Journal of Transport and Land Use, 2019) Cui, Mengying; Levinson, David
    Traditionally accessibility has been analyzed from the perspective of the mean or expected travel time, which fails to capture the full cost, especially the external cost, of travel. The full cost accessibility (FCA) framework, proposed by Cui and Levinson (2018), provides a theoretical basis to fill the gap. It combines temporal, monetary, and non-monetary internal and external travel costs into accessibility evaluations, considering the time cost, crash cost, emission cost, and monetary cost. This paper extends the FCA framework and measures the full cost accessibility by auto for the Minneapolis - St. Paul Metropolitan area, demonstrating the practicality of the FCA framework on real networks.
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    The Safest Path: Analyzing the Effects of Crash Costs on Route Choice and Accessibility
    (2016-08-01) Cui, Mengying; Levinson, David M
    The "safest path" is proposed to optimize the on-road safety of individuals and minimize the cost of crashes. In this study, the framework of a link-based crash cost analysis is built and applied to assess the crash cost of each link segment on the road network of the Minneapolis - St. Paul area based on Safety Performance Functions from the perspective of travelers. The safest path is then found for all OD pairs to compare flow patterns and accessibility distributions with those based on the traditional shortest travel time path. While, the safest path does not coincide with the shortest path, the accessibility distributions have similar patterns.