US Transportation Collection2020PDFTech ReportChavis, CelesteJones, AnitaUrban Mobility & Equ... more US Transportation Collection2020PDFTech ReportChavis, CelesteJones, AnitaUrban Mobility & Equity CenterMorgan State UniversityUniversity of Maryland (College Park, Md.)United States. Department of Transportation. University Transportation Centers (UTC) ProgramUnited States. Department of Transportation. Office of the Assistant Secretary for Research and TechnologyUrban Mobility & Equity CenterBaltimore (Maryland)United StatesAccessibilityChi square distributionsDecision treesFoodHealthIncomeLocationShopping tripsSurveysUrban areasAccessMode choiceEquity (Justice)Food desertFood insecurity69A43551747123Final ReportAs American cities have seen a change in land uses in urban areas, with stores moving to suburban areas increasing the reliance on cars, many urban areas are left with a lack of accessible quality food options. These food insecure areas, commonly known as food deserts, where residents lack both access and sufficient economic resources to purchase healthy food, result in health disparities for residents in these communities. Though the existence of food deserts are well known among researchers, there is a lack of consensus on how food deserts are defined and identified. Through a survey of 573 Baltimore City residents, this study provides an in-depth analysis of individual grocery store choice and travel decisions. The study found that most people grocery shopped 2-4 times in a given month and at 2-3 different grocery stores; the choice of the store depends on the items purchased. In evaluating food desert metrics, two common assumptions are made: (1) trips originate from home and (2) people shop at the nearest store. This study found that the second assumption does not hold as an overwhelming percentage of those surveyed (77%) do not shop at their nearest grocery store. By using the survey data, the authors of this study identified user-generated data-driven indicators with statistical significance for developing a novel food desert metric using CHAID decision trees. A new healthy food priority area measure was developed for Baltimore that deemed all residential areas where the median income of the census block group is less than $35,000 as food insecure. A prioritization matrix was developed based on the secondary factors of proximity to the nearest grocery store (at the half-mile threshold) and the number of stores within 3 miles. This measure found a significant difference in the frequency of grocery store visits as well as the quality of food for those who live in a food desert as opposed to those who do not. The results of this study showed that people value choice of stores when grocery shopping. Limiting food desert measures to the distance to the nearest supermarket undervalues the importance of choice and variety in food selection. The data-driven yet simplistic methodology presented can be replicated to other municipalities as developing an accurate method of prioritizing areas for investments to reduce food disparities is vital to addressing the prevailing systemic divestiture of resources on communities.109
Transportation Research Record: Journal of the Transportation Research Board
A food desert is a geographic area lacking spatial and socioeconomic access to healthy foods. Dis... more A food desert is a geographic area lacking spatial and socioeconomic access to healthy foods. Disparities in food access and availability hinder public health and individual wellbeing. Access to healthy food has been evaluated by many agencies and researches yet they do not comparably demarcate food deserts or identify vulnerable populations in methodical terms. Existing literature suggests a link between food deserts, income level, and vehicle ownership. This study evaluates the existing methods and proposes a novel data-driven method to identify food deserts in Baltimore, Maryland. This study evaluates responses from 573 respondents for an in-depth analysis of individual grocery store choice and travel decisions. Chi-square automatic interaction detector (CHAID) decision trees are used to develop a user-generated food desert metric. Income level is found to be a key indicator for food desert demarcation, more than vehicle ownership. Network distance was applied to develop the prio...
Natural or man-made hazards that require evacuation put already vulnerable populations in a more ... more Natural or man-made hazards that require evacuation put already vulnerable populations in a more precarious situation. When plans and decisions about evacuation are made, access to a private car is typically assumed, and differences in income levels across a community are rarely taken into account. The result is that carless members of a community can find themselves stranded. Low-income carless residents need alternative transportation means to reach shelters in case of an emergency. Thus, evacuation plans, decisions, and models need necessary information that identifies and locates these populations. In this study, data from the American Community Survey, U.S. Census, Internal Revenue Service, and the National Household Travel Survey are used to generate a synthetic population for Anne Arundel County, Maryland, using the copula concept. Geographic locations of low-income residents are identified within each subarea of the county (census tract) and their car ownership is estimated ...
Buses stopping at transit stops reduce the capacity of signalized intersections, which can lead t... more Buses stopping at transit stops reduce the capacity of signalized intersections, which can lead to excessive delays for all users. In order to avoid such phenomena signal control strategies can be used. This paper presents a signal control strategy to mitigate the impact of bus stop operations on traffic operations along an undersaturated approach. The objective of the proposed strategy is to increase the green time for the bus stop approach during the cycle after the bus has left the stop in order to ensure that the residual queue that was created by the presence of the bus at the bus stop can fully dissipate within the following cycle. In addition, this strategy ensures that the cross-street approaches can clear any residuals queues caused by this strategy within a cycle after its implementation. Kinematic wave theory is used to track the formation and dissipation of queues and determine the red truncation (or equivalently green extension). The benefits achieved from the proposed ...
This paper develops a mode choice model that can be used to unveil how transit users select betwe... more This paper develops a mode choice model that can be used to unveil how transit users select between competing transit options. Specifically, the model choice model considers traditional fixed-route transit systems, flexible-route systems in which vehicles are shared but routes are flexible to prevailing demands and individual transit systems (e.g., Uber or Lyft) that provide door-to-door and demand responsive service. A stated preference survey was performed in which survey participants were provided a set of scenarios and asked to select the most attractive transit option of the three previously mentioned. Each scenario was presented using the following attributes: walking time required, waiting time (including variability), in-vehicle travel time (including variability), monetary cost and availability of GPS tracking services. Various statistical modeling frameworks were considered and applied to these survey data to describe the mode choice decision-making process. The results re...
As the number and influence of elderly persons in the United States grows, the changing transport... more As the number and influence of elderly persons in the United States grows, the changing transportation needs of this population will take on increasing importance. According to the National Vital Statistics Report published by the Centers for Disease Control (2013), the life expectancy as of 2010 was 78.7 years, an increase from 77.0 years in 2000. The elderly population will be expected to continue contributing to society as their numbers grow. These contributions will be expected as many opt to limit or cease driving. As a result, a given economy risks losing significant economic contribution due to the mobility loss experienced by elderly persons who do not drive. Health and Retirement Study (HRS) data between 2000 and 2012 were used to determine driving ability. Consumption and Activities Mail Survey (CAMS) data was then used to examine consumption patterns of the study group for certain categories. Driving cessation was shown to be associated with a significant reduction in ove...
US Transportation Collection2020PDFTech ReportChavis, CelesteJones, AnitaUrban Mobility & Equ... more US Transportation Collection2020PDFTech ReportChavis, CelesteJones, AnitaUrban Mobility & Equity CenterMorgan State UniversityUniversity of Maryland (College Park, Md.)United States. Department of Transportation. University Transportation Centers (UTC) ProgramUnited States. Department of Transportation. Office of the Assistant Secretary for Research and TechnologyUrban Mobility & Equity CenterBaltimore (Maryland)United StatesAccessibilityChi square distributionsDecision treesFoodHealthIncomeLocationShopping tripsSurveysUrban areasAccessMode choiceEquity (Justice)Food desertFood insecurity69A43551747123Final ReportAs American cities have seen a change in land uses in urban areas, with stores moving to suburban areas increasing the reliance on cars, many urban areas are left with a lack of accessible quality food options. These food insecure areas, commonly known as food deserts, where residents lack both access and sufficient economic resources to purchase healthy food, result in health disparities for residents in these communities. Though the existence of food deserts are well known among researchers, there is a lack of consensus on how food deserts are defined and identified. Through a survey of 573 Baltimore City residents, this study provides an in-depth analysis of individual grocery store choice and travel decisions. The study found that most people grocery shopped 2-4 times in a given month and at 2-3 different grocery stores; the choice of the store depends on the items purchased. In evaluating food desert metrics, two common assumptions are made: (1) trips originate from home and (2) people shop at the nearest store. This study found that the second assumption does not hold as an overwhelming percentage of those surveyed (77%) do not shop at their nearest grocery store. By using the survey data, the authors of this study identified user-generated data-driven indicators with statistical significance for developing a novel food desert metric using CHAID decision trees. A new healthy food priority area measure was developed for Baltimore that deemed all residential areas where the median income of the census block group is less than $35,000 as food insecure. A prioritization matrix was developed based on the secondary factors of proximity to the nearest grocery store (at the half-mile threshold) and the number of stores within 3 miles. This measure found a significant difference in the frequency of grocery store visits as well as the quality of food for those who live in a food desert as opposed to those who do not. The results of this study showed that people value choice of stores when grocery shopping. Limiting food desert measures to the distance to the nearest supermarket undervalues the importance of choice and variety in food selection. The data-driven yet simplistic methodology presented can be replicated to other municipalities as developing an accurate method of prioritizing areas for investments to reduce food disparities is vital to addressing the prevailing systemic divestiture of resources on communities.109
Transportation Research Record: Journal of the Transportation Research Board
A food desert is a geographic area lacking spatial and socioeconomic access to healthy foods. Dis... more A food desert is a geographic area lacking spatial and socioeconomic access to healthy foods. Disparities in food access and availability hinder public health and individual wellbeing. Access to healthy food has been evaluated by many agencies and researches yet they do not comparably demarcate food deserts or identify vulnerable populations in methodical terms. Existing literature suggests a link between food deserts, income level, and vehicle ownership. This study evaluates the existing methods and proposes a novel data-driven method to identify food deserts in Baltimore, Maryland. This study evaluates responses from 573 respondents for an in-depth analysis of individual grocery store choice and travel decisions. Chi-square automatic interaction detector (CHAID) decision trees are used to develop a user-generated food desert metric. Income level is found to be a key indicator for food desert demarcation, more than vehicle ownership. Network distance was applied to develop the prio...
Natural or man-made hazards that require evacuation put already vulnerable populations in a more ... more Natural or man-made hazards that require evacuation put already vulnerable populations in a more precarious situation. When plans and decisions about evacuation are made, access to a private car is typically assumed, and differences in income levels across a community are rarely taken into account. The result is that carless members of a community can find themselves stranded. Low-income carless residents need alternative transportation means to reach shelters in case of an emergency. Thus, evacuation plans, decisions, and models need necessary information that identifies and locates these populations. In this study, data from the American Community Survey, U.S. Census, Internal Revenue Service, and the National Household Travel Survey are used to generate a synthetic population for Anne Arundel County, Maryland, using the copula concept. Geographic locations of low-income residents are identified within each subarea of the county (census tract) and their car ownership is estimated ...
Buses stopping at transit stops reduce the capacity of signalized intersections, which can lead t... more Buses stopping at transit stops reduce the capacity of signalized intersections, which can lead to excessive delays for all users. In order to avoid such phenomena signal control strategies can be used. This paper presents a signal control strategy to mitigate the impact of bus stop operations on traffic operations along an undersaturated approach. The objective of the proposed strategy is to increase the green time for the bus stop approach during the cycle after the bus has left the stop in order to ensure that the residual queue that was created by the presence of the bus at the bus stop can fully dissipate within the following cycle. In addition, this strategy ensures that the cross-street approaches can clear any residuals queues caused by this strategy within a cycle after its implementation. Kinematic wave theory is used to track the formation and dissipation of queues and determine the red truncation (or equivalently green extension). The benefits achieved from the proposed ...
This paper develops a mode choice model that can be used to unveil how transit users select betwe... more This paper develops a mode choice model that can be used to unveil how transit users select between competing transit options. Specifically, the model choice model considers traditional fixed-route transit systems, flexible-route systems in which vehicles are shared but routes are flexible to prevailing demands and individual transit systems (e.g., Uber or Lyft) that provide door-to-door and demand responsive service. A stated preference survey was performed in which survey participants were provided a set of scenarios and asked to select the most attractive transit option of the three previously mentioned. Each scenario was presented using the following attributes: walking time required, waiting time (including variability), in-vehicle travel time (including variability), monetary cost and availability of GPS tracking services. Various statistical modeling frameworks were considered and applied to these survey data to describe the mode choice decision-making process. The results re...
As the number and influence of elderly persons in the United States grows, the changing transport... more As the number and influence of elderly persons in the United States grows, the changing transportation needs of this population will take on increasing importance. According to the National Vital Statistics Report published by the Centers for Disease Control (2013), the life expectancy as of 2010 was 78.7 years, an increase from 77.0 years in 2000. The elderly population will be expected to continue contributing to society as their numbers grow. These contributions will be expected as many opt to limit or cease driving. As a result, a given economy risks losing significant economic contribution due to the mobility loss experienced by elderly persons who do not drive. Health and Retirement Study (HRS) data between 2000 and 2012 were used to determine driving ability. Consumption and Activities Mail Survey (CAMS) data was then used to examine consumption patterns of the study group for certain categories. Driving cessation was shown to be associated with a significant reduction in ove...
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Papers by Celeste Chavis