I am the James R. Cudworth Professor of Department of Civil, Construction & Environmental Engineering at the University of Alabama where I run the Transportation and Human Development Laboratory. I recently completed a year at the Namibia University of Science and Technology as a Fulbright Scholar. My work there included: road safety, inclusive mobility, and young researcher development. Phone: +1 205 348 3137 Address: Department of Civil, Construction & Environmental Engineering/Alabama Transportation Institute Box 870205. 2015 Cyber Hall, The University of Alabama
It is useful to distinguish further between ‘biological violence’, which reduces somatic capabili... more It is useful to distinguish further between ‘biological violence’, which reduces somatic capability below what is potentially possible), and ‘physical violence as such,’ which increases the constraint on human movements—as when a person is imprisoned or put in chains, but also when access to transportation is very unevenly distributed, keeping large segments of a population at the same place with mobility a monopoly of the selected few. Galtung (1969)
A growing body of research has examined the disparities in road traffic safety among population g... more A growing body of research has examined the disparities in road traffic safety among population groups and geographic regions. These studies reveal disparities in crash outcomes between people and regions with different socioeconomic characteristics. A critical aspect of the road traffic crash epidemic that has received limited attention is the influence of local characteristics on human elements that increase the risk of getting into a crash. This paper applies multilevel logistic regression modeling techniques to investigate the influence of driver residential factors on driver behaviors in an attempt to explain the area-based differences in the severity of road crashes across the State of Alabama. Specifically, the paper reports the effects of characteristics attributable to drivers and the geographic regions they reside on the likelihood of a crash resulting in serious injuries. Model estimation revealed that driver residence (postal code or region) accounted for about 7.3% of the variability in the probability of a driver getting into a serious injury crash, regardless of driver characteristics. The results also reveal disparities in serious injury crash rate as well as significant proportions of serious injury crashes involving no seatbelt usage, driving under influence (DUI), unemployed drivers, young drivers, distracted driving, and African American drivers among some regions. The average credit scores, average commute times, and populations of driver postal codes are shown to be significant predictors for risk of severe injury crashes. This approach to traffic crash analysis presented can serve as the foundation for evidence-based policies and also guide the implementation of targeted countermeasures.
This paper studies last train coordination problem for metro networks, aiming to maximize the tot... more This paper studies last train coordination problem for metro networks, aiming to maximize the total number of passengers who can reach their destinations by metro prior to the end of operation. The concept of last boarding time is defined as the latest time that passengers can board the last trains and reach final destinations. The corresponding method for calculating last boarding time is also put forward. With automatic fare collection system data, an optimization model for coordinating last trains is proposed. The objective function optimizes the number of passengers who can reach their final destinations during the train period using departure times and headways of last trains for each line as decision variables. Afterwards, an adaptive genetic algorithm is put forward to solve this model and is applied to a case study of the Shanghai metro system.
Within a broad framework for comprehensive advancement, the Sustainable Development Goals (SDGs) ... more Within a broad framework for comprehensive advancement, the Sustainable Development Goals (SDGs) directly address the importance of safe transport to human development. We analysed some 29 000 crashes recorded in Namibia between 2012 and 2015 to identify connections between road safety and sustainable development there and, by extension, throughout Sub-Saharan Africa and other developing countries. The results indicate that the heavy reliance on transport services for basic mobility, especially in rural areas, contributes to negative development outcomes in terms of significant burden of injuries and death, many of which affect younger people of prime working age. The results also suggest that development pressures such as increased commercial traffic and more private vehicles increase the burden of roadway crashes. Many of the underlying factors contributing to these crashes are attributable to driving behaviours and safety cultures that must be addressed as part of programmatic socioeconomic development in order to mitigate the negative effects of transportation and more fully realise its potential to support sustainable development. We document additional ways in which the provision of safe transport is interrelated to successful attainment of the broader SDGs including those not explicitly addressing safe transport such as 4, 5, 8, 9, 16, and 17.
When autonomous vehicles (AVs) are fully functional, they will compete with existing mainstays in... more When autonomous vehicles (AVs) are fully functional, they will compete with existing mainstays in the transportation system. Sharing AVs can mitigate the inefficient use of privately-owned AVs (e.g., empty-vehicle miles), and to improve the productivity of AVs (i.e., less time parked than personal vehicles). Further, sharing AVs will enable people to travel without vehicle ownership costs and responsibilities. In this regard, taxi travelers will likely be the first users of shared autonomous vehicles (SAVs). This study investigates the trips made by taxi users in Chicago and develops an agent-based modeling framework to simulate a fleet of SAVs operating in the network, competing with human driver taxis. Results show that SAVs may attract more users than conventional taxis because of reduced driver-associated costs (driver not required in SAV services). The results provide insights to both private and public sectors who seek to implement SAVs to challenge or eventually replace existing taxis.
Rural road networks play a fundamental role in the socioeconomic development and poverty alleviat... more Rural road networks play a fundamental role in the socioeconomic development and poverty alleviation in rural regions, especially in developing countries. However, lack of sufficient rural road construction fund is a very common phenomenon in the majority of developing countries. This paper proposes a method for allocating rural roadway construction funding in a more equitable manner. A methodology based on an index composed of a modified Gini coefficient formulation and the population weighted coefficient of variation is proposed to score geographic regions according to: (a) the relative equity of roadway construction to economic development; (b) the relative equity of economic development across populations within a region; and (c) the relative economic strength of individual regions. The methodology is illustrated by a case study of four representative Chinese provinces. The study and results of this paper can be used as a reference for policymakers at central or local levels when planning rural roadway construction fund allocations. Future research is suggested to refine the methodology and to ultimately incorporate it into a stakeholder driven funding allocation process.
In 2013, UN-Habitat released the State of The World's Cities 2012/2013 report introducing the Cit... more In 2013, UN-Habitat released the State of The World's Cities 2012/2013 report introducing the City Prosperity Index (CPI) as a measure to guide urban decision makers. The report asserts that urban prosperity is one of the key human development issues facing the world. Transport is a basic component of urban infrastructure and is essential to urban prosperity. Urban transport system users in a given area comprise people with diverse background and socioeconomic characteristics including different ages, genders, income ranges, employment status, and experiential knowledge. Effective involvement of diverse urban populations is a necessary prerequisite to sustainable urban transport planning. This paper describes the development of a proposed framework, the Localized Sustainability Score (LSS), for screening urban transport projects based. Specifically, the framework assesses the relative importance of various locally applicable sustainability criteria and maps the ability of candidate urban transport projects to positively impact them. The development of the LSS is described via a case study in Accra, Ghana. Ultimately, the proposed LSS is seen as a useful means of relating transport infrastructure to various sustainability/urban prosperity measures. More specifically, the LSS framework can used to rank and priorities urban transport projects as part of a stakeholder-driven decision-making process. Development and application of the LSS framework does not require extensive collection of quantitative data; it is particularly suited to relating qualitative information (such as that contained in urban prosperity measurements) to the capabilities of urban transport projects to impact them. Continued development and application of the LSS can be used to develop richer understandings of various indices and how they reflect the lives of different demographic groups that make up an urban population. It is hoped that exploratory efforts like the development of the LSS and large-scale programs such as the CPI development by UN-Habitat will continue to draw attention to the need (and indeed capacity) to comprehensively approach urban development issues with a view to increasing urban prosperity.
Transport contributes to socioeconomic development. In the case of rapidly developing and rapidly... more Transport contributes to socioeconomic development. In the case of rapidly developing and rapidly motorizing societies like India, increased mobility brings an increased burden associated with road crashes and their social and economic consequences. The Sustainable Development Goals (SDG) explicitly address road safety as necessary to achieving targets related to good health (SDG 3) but also as part of the targets leading towards more sustainable cities and communities (SDG 11). We apply Seemingly Unrelated Regression to investigate development-related factors that potentially contribute to differences among urban and rural road crash outcomes using open data sets for 35 states and territories in India. Results indicate that there are relationships among development and crash parameters common to both urban and rural areas. Interestingly, the results indicate different development indicators driving differences in crash outcomes in rural versus urban areas. Study findings are supportive of international efforts to better understand complex relationships among the goals and targets set out in the SDGs and other high-level declarations such as the New Urban Agenda. It is hoped this paper adds a new perspective on road safety within sustainable development discussions and encourages interdisciplinary research to further explore these relationships across various regions, countries, and contexts.
Transportation Research Interdisciplinary Perspectives, 2020
The study explores the recent trends in school travel using the 2017 National Household Travel Su... more The study explores the recent trends in school travel using the 2017 National Household Travel Survey data. The study also investigates the exogenous factors affecting the school travel mode choice using random parameters multinomial logit (RPMNL) model. The results indicate that urban school trips range between 3 and 5 miles, whereas, average rural trips are longer than 6 miles. School commute times are higher among lower-income households. Further, the share of school bus and auto has declined while that of walking and biking has increased in 2017. This change is significant among high school students. Like other studies, the findings of the RPMNL model confirm that students within shorter distances from school are more likely to walk or bike to school. However, the likelihood of riding a school bus for distances >15 miles is higher than that of auto, indicating a policy implication to support school transportation budgets, especially in rural school districts. Lower-income households have a higher likelihood of riding the school bus. Females are more likely to use a car and less likely to bike to school. Interestingly, households with more than three vehicles are more likely to use the school bus compared to no-vehicle households. Children living in rented houses are less likely to ride the school bus or car. Also, an increase in gas price is indirectly but positively linked with walking, biking, and auto use. The findings from this study will assist policymakers in formulating policies and planning decisions towards improvements in the current school travel trends.
As part of broader research efforts to understand the factors contributing to crashes involving y... more As part of broader research efforts to understand the factors contributing to crashes involving younger drivers, it is important to characterize the crash contributing factors of the at-fault younger drivers. This study applied latent class analysis (LCA) to identify subgroups with statistically distinct patterns in the contributing factors of fatal crashes involving young male and female drivers in Alabama. Model estimation results reveal that crashes on rural roads are a serious issue in Alabama. It was also observed that a high proportion of the young driver fatal crashes occurred on weekends and closer to the driver's place of residence. Interestingly, the proportion of crashes involving speeding increased with age for males and decreased with age for females. In general, younger female drivers (15-18 years) were more likely to be involved in speed and aggressive driving related fatal crashes than their male counterparts. Also, fatal crashes involving driving under influence (DUI) increase with age for both male and female drivers, with a significant increase for drivers between 19 and 21 years of age. These study findings suggest that specific attention should be focused towards younger drivers in rural communities and communities with lower socioeconomic opportunities. Targeted education and outreach campaigns, combined with appropriate enforcement efforts could meaningfully change the attitudes and behaviors related to road safety.
Factors related to drivers and their driving habits dominate the causation of traffic crashes. An... more Factors related to drivers and their driving habits dominate the causation of traffic crashes. An in-depth understanding of the human factors that influence risky driving could be of particular importance to facilitate the application of effective countermeasures. This paper sought to investigate effects of human-centered crash contributing factors on crash outcomes. To select the methodology that best accounts for unobserved heterogeneity between crash outcomes, latent class (LC) logit model and random parameters logit (RPL) model were developed. Model estimation results generally show that serious injury crashes were more likely to involve unemployed drivers, no seatbelt use, old drivers, fatigued driving, and drivers with no valid license. Comparison of model fit statistics shows that the LC logit model outperformed the RPL model, as an alternative to the traditional multinomial logit (MNL) model.
Transit-oriented development (TOD) is a community development strategy that has increasingly gain... more Transit-oriented development (TOD) is a community development strategy that has increasingly gained exposure in urban areas across the United States as a method for reducing urban sprawl and increasing community vitality. Specifically, bikesharing is seen to play a major role in the success of transit-oriented development across urban communities as it increases travel possibilities, encourages public transit connections, and provides opportunities for recreation. This research employed a case study of Zyp BikeShare, a point-to-point bike rental program that began in Birmingham, Alabama, in 2015. We analyzed the bikesharing program in terms of its role in TOD, user catchment areas, transit paths, and usage trends. In doing so, we were able to create a methodology for analyzing specific bikeshare programs. The methodology and lessons could be replicated in assessing bikeshare systems in other cities with similar urban growth and natural characteristics.
Transportation Research Interdisciplinary Perspectives, 2019
Variations that exist in the frequency and severities of crashes across regions may be due to dif... more Variations that exist in the frequency and severities of crashes across regions may be due to differences in road user behaviors or indirectly due to differences in regional characteristics. Regional strategies towards "vision zero" road fatalities , consisting of appropriate safety policies and laws, supported with public education and backed by appropriate sanctions, have the ability to shape road user behaviors in the long term. In this paper, certain human-centered crash factors are viewed as the outcome of a hierarchical system made up of road users nested in regions, in a way that regional characteristics like policies and punitive measures influence road user behaviors. Hence, we propose a multi-level framework that captures driver characteristics and regional attributes that directly and indirectly affect crash outcomes. The concept was applied to crash data analysis for the state of Alabama, where it was found that the probability of a fatal crash involving a typical driver is 0.115. About 6.19% of the variability in the fatal crash rate involving drivers from the state is accounted for by the city and 3.84% is accounted for by the county of residence of the causal driver, leaving 89.97% of the variability to be accounted for by driver attributes or other crash contributing factors. Fatal crash rates varied significantly across the state and some crash factors were more pronounced among drivers from particular cities and counties. In view of these findings, specific countermeasures and structural adjustments may be targeted in locations with the highest proportions of risky driver behaviors.
Public perceptions play a crucial role in wider adoption of autonomous vehicles (AVs). This paper... more Public perceptions play a crucial role in wider adoption of autonomous vehicles (AVs). This paper aims to make two contributions to the understanding of public attitudes toward AVs. First, we explore opinions regarding the perceived benefits and challenges of AVs among vulnerable road users-in particular, pedestrians and bicyclists. Second, the paper evaluated whether interaction experiences with AVs influence perceptions among vulnerable road users. To explore this, we examined survey data collected by Bike PGH, a Pittsburgh based organization involved in programs to promote safe mobility options for road users. Analysis of the data revealed that respondents with direct experience interacting with AVs reported significantly higher expectations of the safety benefits of the transition to AVs than respondents with no AV interaction experience. This finding did not differ across pedestrian and bicyclist respondents. The results of this study indicate that as the public increasingly interacts with AVs, their attitudes toward the technology are more likely to be positive. Thus, this study recommends that policy makers should provide the opportunities for the public to have interaction experience with AVs. The opportunities can be provided through legislation that allows auto manufacturers and technology industries to operate and test AVs on public roads. This interactive experience will positively affect people's perceptions and help in wider adoption of AV technology.
Adaptive traffic control systems (ATCS) continuously adapt to changing traffic in order to improv... more Adaptive traffic control systems (ATCS) continuously adapt to changing traffic in order to improve traffic performance at signalized intersections. Typical before-after studies evaluate the success of ATCS deployments by assessing only the postimplementation traffic performance. Fully assessing the feasibility of ATCS implementation, however, requires evaluating the changes in long-term ATCS performance with changing traffic demands. This paper illustrates the assessment of long-term ATCS performance of two study corridors. The study uses volume=capacity (v=c) ratio to evaluate the effects of changing corridor flow on corridor-wide delay benefits. The results show that the Sydney Coordinated Adaptive Traffic System (SCATS) improves corridor flow and decreases corridor-wide delays up to a point of ineffectiveness, beyond which the ATCS performance begins to decrease. The ineffectiveness point helps in deriving a reasonable estimate for the magnitude and duration of potential ATCS deployment benefits.
Background: Drunk-driving is a major crash risk factor, and crashes resulting from this risky beh... more Background: Drunk-driving is a major crash risk factor, and crashes resulting from this risky behavior tend to be serious and have significant economic and societal impacts. The presence of passengers and their demographics and activities can influence risky driving behaviors such as drunk-driving. However, passengers could either be an "enabling" factor to take more risks or could be an "inhibiting" factor by ensuring safe driving by a drunk-driver. Objective: This study examines whether the presence of passengers affects the contributing factors of single-vehicle (SV) drunk-driving crashes, by presenting a severity analysis of single-and multi-occupant SV drunk-driving crashes, to identify risk factors that contribute to crash severity outcomes, for the effective implementation of relevant countermeasures. Method: A total of 7407 observations for 2012-2016 from the crash database of the State of Alabama was used for this study. The variables were divided into six classes: temporal, locational, driver, vehicle, roadway, and crash characteristics and injury severities into three: severe, minor, and no injury. Two latent class multinomial logit models-one each for single-and multi-occupant crashes-were developed, to analyze the effects of significant factors on injury severity outcomes using marginal effects. Results: The estimated results show that collision with a ditch, runoff road, intersection, winter season, wet roadway, and interstate decreased the probability of severe injuries in both single-and multi-occupant crashes, whereas rural area, road with downward grade, dark and unlit roadway, unemployed driver, and driver with invalid license increased the likelihood of severe injuries for both single-and multi-occupant crashes. Female drivers were more likely to be severely injured in single-occupant crashes, but less likely in multi-occupant crashes. A significant association was found between severe injuries and weekends, residential areas, and crash location close (<25 mi ≈40.23 km) to the residence of the at-fault driver in multi-occupant crashes. Sport utility vehicles were found to be safer when driving with passengers. Conclusions: The model findings show that, although many correlates are consistent between the single-and multi-occupant SV crashes that are associated with locational, roadway, vehicle, temporal, and driver characteristics, their effect can vary across the single-and multi-occupant driving population. The findings from this study can help in targeting interventions, developing countermeasures, and educating passengers to reduce drunk-driving crashes and consequent injuries. Such integrated efforts combined with engineering and emergency response may contribute in developing a true safe systems approach.
Non-recurrent congestion (NRC) associated with special/unusual events in a community has the pote... more Non-recurrent congestion (NRC) associated with special/unusual events in a community has the potential to cause greater levels of congestion than the typical morning and evening rush hour periods due to the unexpected nature of the congestion and uncertainty of the traffic volumes. Most of the previous research on recurrent and non-recurrent has focused on freeway conditions. This paper presents a brief examination of the impact of non-recurrent congestion along an arterial corridor as it related to data collected during an event. Lane-specific travel time and speed data were collected along a study corridor using probe cars with Global Positioning System receivers. General, route-level observation was not sufficient to identify the effect of non-recurrent congestion on any specific lane. Therefore, Detailed time of day data supported more detailed statistical analyses that showed differences in lane-specific travel times and speeds between the two congestion regimes. It is recommended that future research be conducted to validate the impact of the left turn lane storage length and left turn signal phasing during non-recurrent congestion events. Use of microscopic traffic simulation can be used to perform sensitivity analyses on a range left-turn scenarios (volumes, timing splits, lane lengths, etc.). The results support the need for detailed analyses of probable NRC traffic operations to ensure the most efficient outcomes possible for both RC and NRC in a given corridor.
A novel conditional cell transmission model (CCTM) is a potential simulation tool because it acco... more A novel conditional cell transmission model (CCTM) is a potential simulation tool because it accommodates all traffic conditions from light condition to oversaturated condition. To test the performance of the CCTM, a series of experiments for sensitivity analysis were designed and performed for a multilane, two-way, three-signal sample network. Experiment 1 shows that the model is performed in a logical and expected manner with variations in traffic demand with time and direction. Experiment 2 shows when the possibility of the occurrence of a useful gap increases to 60% and 100%, the delays in left turns decrease by 5% and 15%, respectively. In Experiment 3, comparing the possibility of a conditional cell of 0 with 100%, delay of left turn and delay of the entire network were underestimated by 58% and 11%, respectively. Hence, sensitivity analysis demonstrates that by reflecting local drivers' behaviors properly, the CCTM provides an accurate representation of traffic flow in simulating oversaturated traffic conditions.
It is useful to distinguish further between ‘biological violence’, which reduces somatic capabili... more It is useful to distinguish further between ‘biological violence’, which reduces somatic capability below what is potentially possible), and ‘physical violence as such,’ which increases the constraint on human movements—as when a person is imprisoned or put in chains, but also when access to transportation is very unevenly distributed, keeping large segments of a population at the same place with mobility a monopoly of the selected few. Galtung (1969)
A growing body of research has examined the disparities in road traffic safety among population g... more A growing body of research has examined the disparities in road traffic safety among population groups and geographic regions. These studies reveal disparities in crash outcomes between people and regions with different socioeconomic characteristics. A critical aspect of the road traffic crash epidemic that has received limited attention is the influence of local characteristics on human elements that increase the risk of getting into a crash. This paper applies multilevel logistic regression modeling techniques to investigate the influence of driver residential factors on driver behaviors in an attempt to explain the area-based differences in the severity of road crashes across the State of Alabama. Specifically, the paper reports the effects of characteristics attributable to drivers and the geographic regions they reside on the likelihood of a crash resulting in serious injuries. Model estimation revealed that driver residence (postal code or region) accounted for about 7.3% of the variability in the probability of a driver getting into a serious injury crash, regardless of driver characteristics. The results also reveal disparities in serious injury crash rate as well as significant proportions of serious injury crashes involving no seatbelt usage, driving under influence (DUI), unemployed drivers, young drivers, distracted driving, and African American drivers among some regions. The average credit scores, average commute times, and populations of driver postal codes are shown to be significant predictors for risk of severe injury crashes. This approach to traffic crash analysis presented can serve as the foundation for evidence-based policies and also guide the implementation of targeted countermeasures.
This paper studies last train coordination problem for metro networks, aiming to maximize the tot... more This paper studies last train coordination problem for metro networks, aiming to maximize the total number of passengers who can reach their destinations by metro prior to the end of operation. The concept of last boarding time is defined as the latest time that passengers can board the last trains and reach final destinations. The corresponding method for calculating last boarding time is also put forward. With automatic fare collection system data, an optimization model for coordinating last trains is proposed. The objective function optimizes the number of passengers who can reach their final destinations during the train period using departure times and headways of last trains for each line as decision variables. Afterwards, an adaptive genetic algorithm is put forward to solve this model and is applied to a case study of the Shanghai metro system.
Within a broad framework for comprehensive advancement, the Sustainable Development Goals (SDGs) ... more Within a broad framework for comprehensive advancement, the Sustainable Development Goals (SDGs) directly address the importance of safe transport to human development. We analysed some 29 000 crashes recorded in Namibia between 2012 and 2015 to identify connections between road safety and sustainable development there and, by extension, throughout Sub-Saharan Africa and other developing countries. The results indicate that the heavy reliance on transport services for basic mobility, especially in rural areas, contributes to negative development outcomes in terms of significant burden of injuries and death, many of which affect younger people of prime working age. The results also suggest that development pressures such as increased commercial traffic and more private vehicles increase the burden of roadway crashes. Many of the underlying factors contributing to these crashes are attributable to driving behaviours and safety cultures that must be addressed as part of programmatic socioeconomic development in order to mitigate the negative effects of transportation and more fully realise its potential to support sustainable development. We document additional ways in which the provision of safe transport is interrelated to successful attainment of the broader SDGs including those not explicitly addressing safe transport such as 4, 5, 8, 9, 16, and 17.
When autonomous vehicles (AVs) are fully functional, they will compete with existing mainstays in... more When autonomous vehicles (AVs) are fully functional, they will compete with existing mainstays in the transportation system. Sharing AVs can mitigate the inefficient use of privately-owned AVs (e.g., empty-vehicle miles), and to improve the productivity of AVs (i.e., less time parked than personal vehicles). Further, sharing AVs will enable people to travel without vehicle ownership costs and responsibilities. In this regard, taxi travelers will likely be the first users of shared autonomous vehicles (SAVs). This study investigates the trips made by taxi users in Chicago and develops an agent-based modeling framework to simulate a fleet of SAVs operating in the network, competing with human driver taxis. Results show that SAVs may attract more users than conventional taxis because of reduced driver-associated costs (driver not required in SAV services). The results provide insights to both private and public sectors who seek to implement SAVs to challenge or eventually replace existing taxis.
Rural road networks play a fundamental role in the socioeconomic development and poverty alleviat... more Rural road networks play a fundamental role in the socioeconomic development and poverty alleviation in rural regions, especially in developing countries. However, lack of sufficient rural road construction fund is a very common phenomenon in the majority of developing countries. This paper proposes a method for allocating rural roadway construction funding in a more equitable manner. A methodology based on an index composed of a modified Gini coefficient formulation and the population weighted coefficient of variation is proposed to score geographic regions according to: (a) the relative equity of roadway construction to economic development; (b) the relative equity of economic development across populations within a region; and (c) the relative economic strength of individual regions. The methodology is illustrated by a case study of four representative Chinese provinces. The study and results of this paper can be used as a reference for policymakers at central or local levels when planning rural roadway construction fund allocations. Future research is suggested to refine the methodology and to ultimately incorporate it into a stakeholder driven funding allocation process.
In 2013, UN-Habitat released the State of The World's Cities 2012/2013 report introducing the Cit... more In 2013, UN-Habitat released the State of The World's Cities 2012/2013 report introducing the City Prosperity Index (CPI) as a measure to guide urban decision makers. The report asserts that urban prosperity is one of the key human development issues facing the world. Transport is a basic component of urban infrastructure and is essential to urban prosperity. Urban transport system users in a given area comprise people with diverse background and socioeconomic characteristics including different ages, genders, income ranges, employment status, and experiential knowledge. Effective involvement of diverse urban populations is a necessary prerequisite to sustainable urban transport planning. This paper describes the development of a proposed framework, the Localized Sustainability Score (LSS), for screening urban transport projects based. Specifically, the framework assesses the relative importance of various locally applicable sustainability criteria and maps the ability of candidate urban transport projects to positively impact them. The development of the LSS is described via a case study in Accra, Ghana. Ultimately, the proposed LSS is seen as a useful means of relating transport infrastructure to various sustainability/urban prosperity measures. More specifically, the LSS framework can used to rank and priorities urban transport projects as part of a stakeholder-driven decision-making process. Development and application of the LSS framework does not require extensive collection of quantitative data; it is particularly suited to relating qualitative information (such as that contained in urban prosperity measurements) to the capabilities of urban transport projects to impact them. Continued development and application of the LSS can be used to develop richer understandings of various indices and how they reflect the lives of different demographic groups that make up an urban population. It is hoped that exploratory efforts like the development of the LSS and large-scale programs such as the CPI development by UN-Habitat will continue to draw attention to the need (and indeed capacity) to comprehensively approach urban development issues with a view to increasing urban prosperity.
Transport contributes to socioeconomic development. In the case of rapidly developing and rapidly... more Transport contributes to socioeconomic development. In the case of rapidly developing and rapidly motorizing societies like India, increased mobility brings an increased burden associated with road crashes and their social and economic consequences. The Sustainable Development Goals (SDG) explicitly address road safety as necessary to achieving targets related to good health (SDG 3) but also as part of the targets leading towards more sustainable cities and communities (SDG 11). We apply Seemingly Unrelated Regression to investigate development-related factors that potentially contribute to differences among urban and rural road crash outcomes using open data sets for 35 states and territories in India. Results indicate that there are relationships among development and crash parameters common to both urban and rural areas. Interestingly, the results indicate different development indicators driving differences in crash outcomes in rural versus urban areas. Study findings are supportive of international efforts to better understand complex relationships among the goals and targets set out in the SDGs and other high-level declarations such as the New Urban Agenda. It is hoped this paper adds a new perspective on road safety within sustainable development discussions and encourages interdisciplinary research to further explore these relationships across various regions, countries, and contexts.
Transportation Research Interdisciplinary Perspectives, 2020
The study explores the recent trends in school travel using the 2017 National Household Travel Su... more The study explores the recent trends in school travel using the 2017 National Household Travel Survey data. The study also investigates the exogenous factors affecting the school travel mode choice using random parameters multinomial logit (RPMNL) model. The results indicate that urban school trips range between 3 and 5 miles, whereas, average rural trips are longer than 6 miles. School commute times are higher among lower-income households. Further, the share of school bus and auto has declined while that of walking and biking has increased in 2017. This change is significant among high school students. Like other studies, the findings of the RPMNL model confirm that students within shorter distances from school are more likely to walk or bike to school. However, the likelihood of riding a school bus for distances >15 miles is higher than that of auto, indicating a policy implication to support school transportation budgets, especially in rural school districts. Lower-income households have a higher likelihood of riding the school bus. Females are more likely to use a car and less likely to bike to school. Interestingly, households with more than three vehicles are more likely to use the school bus compared to no-vehicle households. Children living in rented houses are less likely to ride the school bus or car. Also, an increase in gas price is indirectly but positively linked with walking, biking, and auto use. The findings from this study will assist policymakers in formulating policies and planning decisions towards improvements in the current school travel trends.
As part of broader research efforts to understand the factors contributing to crashes involving y... more As part of broader research efforts to understand the factors contributing to crashes involving younger drivers, it is important to characterize the crash contributing factors of the at-fault younger drivers. This study applied latent class analysis (LCA) to identify subgroups with statistically distinct patterns in the contributing factors of fatal crashes involving young male and female drivers in Alabama. Model estimation results reveal that crashes on rural roads are a serious issue in Alabama. It was also observed that a high proportion of the young driver fatal crashes occurred on weekends and closer to the driver's place of residence. Interestingly, the proportion of crashes involving speeding increased with age for males and decreased with age for females. In general, younger female drivers (15-18 years) were more likely to be involved in speed and aggressive driving related fatal crashes than their male counterparts. Also, fatal crashes involving driving under influence (DUI) increase with age for both male and female drivers, with a significant increase for drivers between 19 and 21 years of age. These study findings suggest that specific attention should be focused towards younger drivers in rural communities and communities with lower socioeconomic opportunities. Targeted education and outreach campaigns, combined with appropriate enforcement efforts could meaningfully change the attitudes and behaviors related to road safety.
Factors related to drivers and their driving habits dominate the causation of traffic crashes. An... more Factors related to drivers and their driving habits dominate the causation of traffic crashes. An in-depth understanding of the human factors that influence risky driving could be of particular importance to facilitate the application of effective countermeasures. This paper sought to investigate effects of human-centered crash contributing factors on crash outcomes. To select the methodology that best accounts for unobserved heterogeneity between crash outcomes, latent class (LC) logit model and random parameters logit (RPL) model were developed. Model estimation results generally show that serious injury crashes were more likely to involve unemployed drivers, no seatbelt use, old drivers, fatigued driving, and drivers with no valid license. Comparison of model fit statistics shows that the LC logit model outperformed the RPL model, as an alternative to the traditional multinomial logit (MNL) model.
Transit-oriented development (TOD) is a community development strategy that has increasingly gain... more Transit-oriented development (TOD) is a community development strategy that has increasingly gained exposure in urban areas across the United States as a method for reducing urban sprawl and increasing community vitality. Specifically, bikesharing is seen to play a major role in the success of transit-oriented development across urban communities as it increases travel possibilities, encourages public transit connections, and provides opportunities for recreation. This research employed a case study of Zyp BikeShare, a point-to-point bike rental program that began in Birmingham, Alabama, in 2015. We analyzed the bikesharing program in terms of its role in TOD, user catchment areas, transit paths, and usage trends. In doing so, we were able to create a methodology for analyzing specific bikeshare programs. The methodology and lessons could be replicated in assessing bikeshare systems in other cities with similar urban growth and natural characteristics.
Transportation Research Interdisciplinary Perspectives, 2019
Variations that exist in the frequency and severities of crashes across regions may be due to dif... more Variations that exist in the frequency and severities of crashes across regions may be due to differences in road user behaviors or indirectly due to differences in regional characteristics. Regional strategies towards "vision zero" road fatalities , consisting of appropriate safety policies and laws, supported with public education and backed by appropriate sanctions, have the ability to shape road user behaviors in the long term. In this paper, certain human-centered crash factors are viewed as the outcome of a hierarchical system made up of road users nested in regions, in a way that regional characteristics like policies and punitive measures influence road user behaviors. Hence, we propose a multi-level framework that captures driver characteristics and regional attributes that directly and indirectly affect crash outcomes. The concept was applied to crash data analysis for the state of Alabama, where it was found that the probability of a fatal crash involving a typical driver is 0.115. About 6.19% of the variability in the fatal crash rate involving drivers from the state is accounted for by the city and 3.84% is accounted for by the county of residence of the causal driver, leaving 89.97% of the variability to be accounted for by driver attributes or other crash contributing factors. Fatal crash rates varied significantly across the state and some crash factors were more pronounced among drivers from particular cities and counties. In view of these findings, specific countermeasures and structural adjustments may be targeted in locations with the highest proportions of risky driver behaviors.
Public perceptions play a crucial role in wider adoption of autonomous vehicles (AVs). This paper... more Public perceptions play a crucial role in wider adoption of autonomous vehicles (AVs). This paper aims to make two contributions to the understanding of public attitudes toward AVs. First, we explore opinions regarding the perceived benefits and challenges of AVs among vulnerable road users-in particular, pedestrians and bicyclists. Second, the paper evaluated whether interaction experiences with AVs influence perceptions among vulnerable road users. To explore this, we examined survey data collected by Bike PGH, a Pittsburgh based organization involved in programs to promote safe mobility options for road users. Analysis of the data revealed that respondents with direct experience interacting with AVs reported significantly higher expectations of the safety benefits of the transition to AVs than respondents with no AV interaction experience. This finding did not differ across pedestrian and bicyclist respondents. The results of this study indicate that as the public increasingly interacts with AVs, their attitudes toward the technology are more likely to be positive. Thus, this study recommends that policy makers should provide the opportunities for the public to have interaction experience with AVs. The opportunities can be provided through legislation that allows auto manufacturers and technology industries to operate and test AVs on public roads. This interactive experience will positively affect people's perceptions and help in wider adoption of AV technology.
Adaptive traffic control systems (ATCS) continuously adapt to changing traffic in order to improv... more Adaptive traffic control systems (ATCS) continuously adapt to changing traffic in order to improve traffic performance at signalized intersections. Typical before-after studies evaluate the success of ATCS deployments by assessing only the postimplementation traffic performance. Fully assessing the feasibility of ATCS implementation, however, requires evaluating the changes in long-term ATCS performance with changing traffic demands. This paper illustrates the assessment of long-term ATCS performance of two study corridors. The study uses volume=capacity (v=c) ratio to evaluate the effects of changing corridor flow on corridor-wide delay benefits. The results show that the Sydney Coordinated Adaptive Traffic System (SCATS) improves corridor flow and decreases corridor-wide delays up to a point of ineffectiveness, beyond which the ATCS performance begins to decrease. The ineffectiveness point helps in deriving a reasonable estimate for the magnitude and duration of potential ATCS deployment benefits.
Background: Drunk-driving is a major crash risk factor, and crashes resulting from this risky beh... more Background: Drunk-driving is a major crash risk factor, and crashes resulting from this risky behavior tend to be serious and have significant economic and societal impacts. The presence of passengers and their demographics and activities can influence risky driving behaviors such as drunk-driving. However, passengers could either be an "enabling" factor to take more risks or could be an "inhibiting" factor by ensuring safe driving by a drunk-driver. Objective: This study examines whether the presence of passengers affects the contributing factors of single-vehicle (SV) drunk-driving crashes, by presenting a severity analysis of single-and multi-occupant SV drunk-driving crashes, to identify risk factors that contribute to crash severity outcomes, for the effective implementation of relevant countermeasures. Method: A total of 7407 observations for 2012-2016 from the crash database of the State of Alabama was used for this study. The variables were divided into six classes: temporal, locational, driver, vehicle, roadway, and crash characteristics and injury severities into three: severe, minor, and no injury. Two latent class multinomial logit models-one each for single-and multi-occupant crashes-were developed, to analyze the effects of significant factors on injury severity outcomes using marginal effects. Results: The estimated results show that collision with a ditch, runoff road, intersection, winter season, wet roadway, and interstate decreased the probability of severe injuries in both single-and multi-occupant crashes, whereas rural area, road with downward grade, dark and unlit roadway, unemployed driver, and driver with invalid license increased the likelihood of severe injuries for both single-and multi-occupant crashes. Female drivers were more likely to be severely injured in single-occupant crashes, but less likely in multi-occupant crashes. A significant association was found between severe injuries and weekends, residential areas, and crash location close (<25 mi ≈40.23 km) to the residence of the at-fault driver in multi-occupant crashes. Sport utility vehicles were found to be safer when driving with passengers. Conclusions: The model findings show that, although many correlates are consistent between the single-and multi-occupant SV crashes that are associated with locational, roadway, vehicle, temporal, and driver characteristics, their effect can vary across the single-and multi-occupant driving population. The findings from this study can help in targeting interventions, developing countermeasures, and educating passengers to reduce drunk-driving crashes and consequent injuries. Such integrated efforts combined with engineering and emergency response may contribute in developing a true safe systems approach.
Non-recurrent congestion (NRC) associated with special/unusual events in a community has the pote... more Non-recurrent congestion (NRC) associated with special/unusual events in a community has the potential to cause greater levels of congestion than the typical morning and evening rush hour periods due to the unexpected nature of the congestion and uncertainty of the traffic volumes. Most of the previous research on recurrent and non-recurrent has focused on freeway conditions. This paper presents a brief examination of the impact of non-recurrent congestion along an arterial corridor as it related to data collected during an event. Lane-specific travel time and speed data were collected along a study corridor using probe cars with Global Positioning System receivers. General, route-level observation was not sufficient to identify the effect of non-recurrent congestion on any specific lane. Therefore, Detailed time of day data supported more detailed statistical analyses that showed differences in lane-specific travel times and speeds between the two congestion regimes. It is recommended that future research be conducted to validate the impact of the left turn lane storage length and left turn signal phasing during non-recurrent congestion events. Use of microscopic traffic simulation can be used to perform sensitivity analyses on a range left-turn scenarios (volumes, timing splits, lane lengths, etc.). The results support the need for detailed analyses of probable NRC traffic operations to ensure the most efficient outcomes possible for both RC and NRC in a given corridor.
A novel conditional cell transmission model (CCTM) is a potential simulation tool because it acco... more A novel conditional cell transmission model (CCTM) is a potential simulation tool because it accommodates all traffic conditions from light condition to oversaturated condition. To test the performance of the CCTM, a series of experiments for sensitivity analysis were designed and performed for a multilane, two-way, three-signal sample network. Experiment 1 shows that the model is performed in a logical and expected manner with variations in traffic demand with time and direction. Experiment 2 shows when the possibility of the occurrence of a useful gap increases to 60% and 100%, the delays in left turns decrease by 5% and 15%, respectively. In Experiment 3, comparing the possibility of a conditional cell of 0 with 100%, delay of left turn and delay of the entire network were underestimated by 58% and 11%, respectively. Hence, sensitivity analysis demonstrates that by reflecting local drivers' behaviors properly, the CCTM provides an accurate representation of traffic flow in simulating oversaturated traffic conditions.
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