Identification and comparison of crash risk for older drivers

The focus of this research is to identify risk factors for older drivers (drivers of age greater than 65 years) involved in motor vehicle crashes and compare the risk factors with those for other age groups. Developing such risk factors helps in better understanding the causes of crashes involving older drivers. The risk factors are developed based on analyses of network characteristics and other related factors which have an impact on rate of crashes involving older drivers. The factors evaluated include crash severity, collision type, contributing factors, functional class and road class. Other information included in the analyses includes demographic data for the study area by age group, annual vehicle miles of travel, and annual passenger miles of travel by age group. Crash percentages and crash rates based on these factors and measures of exposure are calculated and used to identify risk factors. Descriptive analyses and statistical analyses were used to compare risks across various age groups. The statistical analyses included one-way ANOVA and the Kruskal-Wallis test to compare the crash rates across age groups and to determine the significance of any differences. Data from Clark County, Nevada, are used to demonstrate the application of the methodology; The results from the analysis show that the older drivers, especially those over 75 years of age, have a significantly higher percentage and rate of fatal crashes than those in younger age groups. The analyses based on the collision type show that older drivers have higher proportions of right-turn and left-turn crashes. Based on rates per million vehicle miles of travel (VMT) or per million passenger miles of travel, older drivers have a high proportion of crashes attributed to Failure to yield and Speed related factors. Improper lane change, improper turn, and failure to yield are factors for the older drivers which have higher rates than the average crash rate per million VMT. When functional class is considered, older drivers have higher crash risks on Principal arterials and Minor arterials. The results from analyses based on road characteristics show that the older drivers experience higher proportions of crashes on 6-lane roadways followed by 4-lane roadways. The crash rates appear to be higher on divided roadways than on undivided roadways. These results are valuable in developing strategies to enhance the safety of older drivers in terms of their involvement in motor vehicle crashes. The strategies could focus on education and outreach activities aimed at older drivers as well as engineering design and operational countermeasures.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office