Identification of Risk Factors for Severe Crashes Among Younger and Older Drivers
By Jeff Gooch, Md Shakir Mahmud, Frank Gross & Bonnie Polin
The systemic approach to safety focuses on implementing widely adopted improvements that target high-risk roadway features associated with severe crashes. For instance, a systemic project may implement horizontal curve warning signage, large chevrons, and supplemental delineation on horizontal curves with sharp radii, poor visibility, and high-speed tangent approaches. This approach offers a comprehensive and proactive method for safety planning and implementation, which complements the hot-spot approach to safety management – prioritizing the sites with the largest crash history. The study used systemic safety analysis to identify specific risk factors associated with severe crashes for both younger (24 years and younger) and older (aged 65 and older) drivers. This allows agencies to expand their traffic safety initiatives while accounting for both risk factors and crash history when determining suitable locations for cost-effective safety enhancements.
Fatal crashes involving younger and older drivers are a nationwide concern, accounting for 9% (3,051 fatalities) and 17% (9,102 fatalities) of total traffic fatalities in 2021, respectively. Given the concern associated with younger and older driver involved crashes, the study aimed to identify critical, high-risk locations within Massachusetts. The study used crash (from 2017 to 2021), roadway, driver license, citation, healthy aging, land use, population, environmental justice, and other data sources to analyze the characteristics of severe crashes involving younger and older drivers.
The analysis first identified overrepresented crash attributes (i.e., those attributes which accounted for a higher proportion of severe younger or older driver crashes compared to all severe crashes) in younger and older driver crash databases. This was followed by developing statistical regression models to determine what factors were most correlated with the frequency of severe younger and older driver crashes. The factors identified in the models were used to assign risk scores to the 351 towns in Massachusetts. The risk scores functioned as a surrogate measure for the likelihood that the town will experience a high number of severe younger or older driver crashes in future years. For prioritization, Massachusetts labeled the top 5% of towns by risk score as “Primary Risk Towns” and the next 10% of towns as “Secondary Risk Towns”. Finally, the findings were validated by comparing them with the severe crash frequency of the identified towns, with successful validation indicated by the Primary Risk Towns accommodating significantly more than 5% of the severe target crashes.
From statistical models, the study found that the risk factors for severe crashes differed by driver age group, reflecting the differences in exposure, risk-taking behaviors, and infrastructure characteristics.
For older drivers, the risk factors included:
Presence of older drivers in town;
Healthy aging indicators, such as reported cognitive issues and the presence of assisted living and senior care providers;
Risk-taking behaviors, such as impaired driving and speeding; and
Presence of high-speed facilities, such as interstate, freeway, or expressway.
For younger drivers, the risk factors included:
Presence of young drivers in town;
Risk-taking behaviors, such as unbelted citations, impaired driving citations, and observed unbelted occupants;
Presence of high-speed facilities, such as interstate, freeway, or expressway; and
Historically underinvested infrastructure, such as environmental justice communities.
The study used the model results to develop and apply risk scores to 351 towns in Massachusetts, resulting in 18 towns in the primary risk category and an additional 35 towns in the secondary risk category. The purpose of these categories is for safety stakeholders focused on younger and older driver crashes to know which communities should be priority communities. In the case of younger drivers, the top five percent of towns categorized as primary risk are associated with approximately 14% of severe younger driver crashes, while the next 10 percent captured an additional 22% of target crashes. For older drivers, the top 5 percent of primary risk towns captured approximately 15% of severe older driver crashes, and the next 10 percent captured an additional 20% of target crashes. This indicates the risk scoring models are capturing risk (measured as a notably higher proportion of target crashes than proportion of towns), and thus are valid for use in prioritization.
The study demonstrates the usefulness of the systemic approach to safety, which can help prioritize the areas that need the most attention and intervention based on roadway features that contribute to severe crashes. Our findings highlight the necessity of age-specific and community-level interventions to improve road safety. For younger drivers, strategies such as graduated licensing programs, which limit nighttime driving and the number of passengers, can be effective. For older drivers, redesigning intersections to reduce complexity and offering refresher driving courses can help mitigate risks. The work described here helps Massachusetts prioritize communities for such strategies. Our study identifies community-level factors which seem to correlate with increased severe crash frequency for younger and older drivers, as well as reinforces the need for public awareness campaigns and community-based programs to emphasize safe driving behaviors.
About the Article
Identification of Risk Factors for Severe Younger and Older Driver Crashes in Massachusetts
Jeff Gooch, Md Shakir Mahmud, Frank Gross & Bonnie Polin
First published July 24, 2024
DOI: 10.1177/03611981241253586
Transportation Research Record: Journal of the Transportation Research Board
About the Authors