Turner-Fairbank Highway Research Center

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Investigating Factors That Contribute to Freeway Crash Severity Using Machine Learning

Product Type

Journal Article


Amirreza Nickkar, Ali Yazdizadeh, and Young-Jae Lee



Full citation

Nickkar, A., Yazdizadeh, A., Lee, Y.J. (2020). Investigating Factors That Contribute to Freeway Crash Severity Using Machine Learning. Advances in Transportation Studies, (52), pp 131-142.


While the cost of crashes nears $1 trillion a year in the U.S., the availability of high-resolution Highway Safety Information System (HSIS) data allows researchers to conduct an in-depth analysis of factors that contribute to crashes, and design appropriate interventions. The current study has two main goals: First, finding possible relationships between contributing factors and the severity of crashes on urban expressways and freeways, and, second, improving the prediction accuracy by using a machine learning approach to classify the crash severity and evaluate the performance of this classifier algorithm. The authors used the crash data on urban expressways and freeways from 2005 to 2015 in the state of Washington provided by HSIS. This study uses the random forest model to predict the severity of crashes based on the attributes. The random forest model was able to predict the severity of crashes with 88.6 % accuracy while the authors observed precision of 89.9%, 62.1%, and 40.1% for classes 1-3, respectively. The authors found that crash type, functional class of road, AADT, and location type played a more important role than other variables in predicting the severity of crashes. Furthermore, lighting conditions, weather, year of the crash, and the road characteristics did not have much effect on the severity of crashes.

Available From

Advances in Transportation Studies

Link To Journal Article

Link not available.


Data mining
Machine learning
Crash severity
Crash analysis

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HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

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Research Reports

A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.

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Technical Summaries

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Safety Analysis Tools

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Other Projects

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