Sungyop Kim

Age and pedestrian injury severity in motor-vehicle crashes : A heteroskedastic logit analysis

This research explores the injury severity of pedestrians in motor-vehicle crashes. It is hypothesized that the variance of unobserved pedestrian characteristics increases with age. In response, a heteroskedastic generalized extreme value model is used. The analysis links explanatory factors with four injury outcomes: fatal, incapacitating, non-incapacitating, and possible or no injury. Police-reported crash data between 1997 and 2000 from North Carolina, USA, are used. The results show that pedestrian age induces heteroskedasticity which affects the probability of fatal injury. The effect grows more pronounced with increasing age past 65. The heteroskedastic model provides a better fit than the multinomial logit model. Notable factors increasing the probability of fatal pedestrian injury: increasing pedestrian age, male driver, intoxicated driver (2.7 times greater probability of fatality), traffic sign, commercial area, darkness with or without streetlights (2-4 times greater probability of fatality), sport-utility vehicle, truck, freeway, two-way divided roadway, speeding-involved, off roadway, motorist turning or backing, both driver and pedestrian at fault, and pedestrian only at fault. Conversely, the probability of a fatal injury decreased: with increasing driver age, during the PM traffic peak, with traffic signal control, in inclement weather, on a curved roadway, at a crosswalk, and when walking along roadway.

Driver-injury severity in single-vehicle crashes in California: A mixed logit analysis of heterogeneity due to age and gender

This research develops a mixed logit model of driver-injury severity in single-vehicle crashes in California. The research especially considers the heterogeneous effects of age and gender. Older drivers (65+ years old) were found to have a random parameter with about half the population having a higher probability of a fatal injury given a crash than the comparison group of 25-64 year olds with all other factors than age kept constant. The other half of the 65+ population had a lower probability of fatal injury. Heterogeneity was also noted in vehicle age, but related to the gender of the driver, with males linked to, on average, a higher probability of fatal injury in a newer vehicle compared with females, all other factors kept constant. These effects lend support to the use of mixed logit models in injury severity research and show age and gender based population heterogeneity. Several other factors were found to significantly increase the probability of fatal injury for drivers in single-vehicle crashes, most notably: male driver, drunk driving, unsafe speed, older driver (65+) driving an older vehicle, and darkness without streetlights.

TRAVEL MODE CHOICE OF THE ELDERLY: EFFECTS OF PERSONAL, HOUSEHOLD, NEIGHBORHOOD, AND TRIP CHARACTERISTICS

The travel patterns and travel mode choice of the elderly are analyzed. The elderly are here defined as those who are both 65 or older and retired. A rapid increase in the older population and their proportion in society has tremendous implications for transportation planning and the policy arena. Previous studies on mode choice have been largely focused on working-age people, and existing studies on the travel mode choice of the elderly are limited to descriptive analyses. A systematic analysis is presented of the mode choice of the elderly and how it relates to activity purpose. It is found that neighborhood and trip characteristics, as well as personal and household characteristics, are associated with the mode choice of this group. For example, the elderly are more likely to use transit if they live within five blocks of a bus stop, and they are more likely to share a ride with others when chaining trips, doing errands, or going to a medical appointment and are less likely to use transit when going shopping or doing errands. The elderly prefer walking when going on recreational or personal trips. Those with a higher income are more likely to drive or carpool. The results shed light on the mode choice of the elderly and contribute to the development of a transportation policy framework that considers the elderly. The results suggest that transportation strategies must move beyond private automobiles to prepare adequately for the increasing number of the elderly in society and their mobility needs.

Analyzing fault in pedestrian–motor vehicle crashes in North Carolina

Crashes between pedestrians and motor vehicles are an important traffic safety concern. This paper explores the assignment of fault in such crashes, where observed factors are associated with pedestrian at fault, driver at fault, or both at fault. The analysis is based on police reported crash data for 1997 through 2000 in North Carolina, U.S.A. The results show that pedestrians are found at fault in 59% of the crashes, drivers in 32%, and both are found at fault in 9%. The results indicate drivers need to take greater notice of pedestrians when drivers are turning, merging, and backing up as these are some of the prime factors associated with the driver being found at fault in a crash. Pedestrians must apply greater caution when crossing streets, waiting to cross, and when walking along roads, as these are correlated with pedestrians being found at fault. The results suggest a need for campaigns focused on positively affecting pedestrian street-crossing behavior in combination with added jaywalking enforcement. The results also indicate that campaigns to increase the use of pedestrian visibility improvements at night can have a significant positive impact on traffic safety. Intoxication is a concern and the results show that it is not only driver intoxication that is affecting safety, but also pedestrian intoxication. The findings show in combination with other research in the field, that results from traffic safety studies are not necessarily transferable between distant geographic locations, and that location-specific safety research needs to take place. It is also important to further study the specific effects of the design of the pedestrian environment on safety, e.g. crosswalk spacing, signal timings, etc., which together may affect pedestrian safety and pedestrian behavior.

The exposure of disadvantaged populations in freeway air-pollution sheds: a case study of the Seattle and Portland regions

Freeway-related air pollution and its harmful health risks have been observed in recent research in the environmental-health sciences. In this study we investigate the impact of freeway and arterial-road air pollution on vulnerable populations—for example, the poor, minorities, children, and the elderly—whose housing options are limited. Because many mobile-source emissions decay rapidly with distance, approaching background concentrations at 330 ft from the freeway, populations living near limited access roads are most at risk from exposure. Furthermore, microscale air monitoring systems are rarely in place at these locations in the United States. In this research we will define freeway air-pollution sheds with the aid of a geographic information system analysis and determine populations that may be at risk from exposure to mobile-source pollutants in two West Coast metropolitan areas (Seattle and Portland). We then use cluster analysis to identify key neighborhoods at risk in Seattle. Subsequently, we apply a hedonic pricing model to understand the extent to which house price values in Seattle are related to freeway proximity. Finally, we discuss policy options, planning implications, and mitigation measures, including an assessment of air-quality monitoring needs and land-use prescriptions.

Analysis of Elderly Mobility by Structural Equation Modeling

Mobility is a critical element of quality of life. This is as true for the elderly population as for the larger population. The elderly often have limited physical abilities and financial constraints that might reduce their mobility. Helping the growing elderly population to maintain decent mobility is a critical challenge for transportation planning and policy. For this, the factors that influence the mobility of the elderly population (elderly mobility) must be understood. Only a few systematic studies, however, have been published. Descriptive statistics of the potentially influential factors make it difficult to assess their effects on elderly mobility. The transportation mobility of retired people age 65 years or older in the Puget Sound region of Washington State was analyzed by using a structural equation model. The statistical significance and relative effects of various personal and household characteristics and urban form on elderly mobility were tested. The structural equation model finds statistically significant relationships between age, gender, transportation disability, possession of a drivers license, and education level and elderly mobility. Among these variables, age and education level show the strongest effects. Urban form, however, seems to be insignificant.

Transportation alternatives of the elderly after driving cessation

Rapid growth of the older population poses a significant challenge in transportation. This study investigated stated transportation alternatives of the elderly, age 65 and older, when they can no longer drive; the data are from a national survey conducted by the American Association of Retired Persons in 2004. Using a multinomial logit model, this study analyzed various personal, household, and neighborhood environmental factors associated with transportation alternatives. The study found that getting a ride was the most preferred mode of transportation, regardless of the residential environment. Females were less likely to consider public transit or walking as their preferred transportation alternatives when they could no longer drive, and Hispanics were more likely to consider public transit as their alternative. The elderly with high incomes had a higher propensity toward walking when they were no longer able to drive. Walking was more popular among urban elderly residents. Public transit accessibility increased the propensity toward public transit use, and greater accessibility to activity locations within walking distance increased the propensity toward walking. Finally, the elderly were less likely to consider public transit and walking as their alternatives when they ceased driving if they had never been without transportation.

Analysis of teenage seat belt use: From the 2007 Missouri high school seat belt survey

INTRODUCTIONnThis study analyzed high school teenagers seat belt use based on the observational surveys of more than 15,000 teenagers at 150 schools and was conducted in the state of Missouri, U.S., in 2007. Since fatal car accidents involving high school teenagers are disproportionately high, and increased seat belt use saves lives in what would otherwise be fatal accidents, it is imperative that teenagers safety be protected through an increase in use.nnnMETHODnThis study investigated various personal, vehicle, school, and locational factors associated with high school teenagers seat belt use. Descriptive and binary logit analyses were conducted.nnnRESULTSnWe find that low seat belt use is associated with males, African-Americans, pick-up trucks, accompanying occupants, weekends, inclement driving conditions, small size of school, lower socio-economic status, and rural county school locations. Several factors influencing teenage seat belt use are quite similar to those affecting adult seat belt use, in addition to certain risky behaviors to which teenagers are prone, supporting the importance of early intervention.nnnCONCLUSIONSnPrograms in schools, the adoption of primary seat belt laws, GDL provisions requiring seat belt use, targeted education and campaign efforts for African-American teenagers, seat belt reminder systems, and more resources for rural counties on safety education and enforcement may help increase seat belt use in this vulnerable age group, though other research questions are implied.

Transportation in an Aging Society. Linkage Between Transportation and Quality of Life

This paper explores the effect of transportation factors on the quality of life of older people (those ages 65 years and older). The data are drawn from a national telephone survey done by the American Association of Retired Persons. Exploratory factor analysis was used to develop a quality-of-life index based on five survey questions. Linear regression was used to explore the correlation of the quality-of-life index to transportation as well as various personal, household, and community characteristics. The results showed that low socioeconomic status and a limited social network were linked with a lower quality of life. Various transportation factors were also found to be significant. A lack of transportation in general and, especially, not being a driver were found to be significant factors negatively associated with quality of life. A built environment, which facilitates walking, was found to be positively associated with quality of life. This study finds that accessibility to alternative transportation is positively associated with the quality of life of older people. Specifically, information about transportation options and transportation alternatives for those with disabilities and health problems were found to be significant for the quality of life of older people. This finding indicates that development of transportation alternatives, along with improved accessibility and visibility, is critical for the quality of life of older people in an aging society.

Factors Affecting Common Vehicle-to-Vehicle Collision Types: Road Safety Priorities in an Aging Society

The number of older drivers (65+ years old) is increasing as a result of the baby boom generation reaching retirement age and an increase in drivers license holders among the elderly. The types of collisions incurred by older drivers are compared with those of drivers 30 to 60 years old in vehicle-to-vehicle collisions using the General Estimates System 2002-2003 sampling of reported motor vehicle collisions compiled by the NHTSA National Center for Statistics and Analysis. Multinomial logit vehicle-to-vehicle collision outcome models that account for driver, vehicle, roadway, environmental, and temporal characteristics were created for drivers age 65 and older and a comparison group of drivers 30 to 60 years old. The older drivers are significantly more prone to collisions related to vehicle turning and intersecting paths—particularly at signalized intersections—than are 30-to-60-year-old drivers. As a factor, age is elastic for same-direction and vehicle-turning crashes. Probability decreases with age ...