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Dr. David M. Levinson

Persistent link for this collectionhttps://hdl.handle.net/11299/179806

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Browsing Dr. David M. Levinson by Author "Cui, Mengying"

Now showing 1 - 7 of 7
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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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    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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    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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    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.